Koichi Hirose

"You are much more cowardly than a normal person and easily give in under pressure, but when push comes to shove you can be quite courageous."

- Rohan Kishibe describing Koichi's character.

Koichi Hirose (広瀬 康一) is a side character and ally featured primarily in Diamond Is Unbreakable and appearing briefly in Vento Aureo.

Koichi is a meek high-school freshman who finds himself embroiled in the world of Stand users as he befriends Josuke Higashikata.

Appearance
Koichi is a teenage boy of average build, 157 cm (5'2") tall, though he's depicted as shorter than that. He wears a notably unmodified student uniform, otherwise preferring leisure wear.

Koichi first keeps his light hair neatly combed back. During his confrontation with Tamami, it gains the tendency to rise into spikes when he is excited (producing a look similar to that of Dragon Ball Z character Gohan at Super Saiyan 2 during the Cell Games). Towards the end of his confrontation with Yukako he suddenly cuts his hair, producing a flat-top, which spontaneously grows out again into spikes during his battle with Yoshikage Kira. The color of his hair varies throughout medias, the most common schemes being blond, blue, or silver.

Heaven's Door reveals that Koichi was born prematurely weighing only 2325 grams (5 lbs 2 oz), and was kept in intensive care for 7 days.

Personality
Koichi is an amiable but meek youth who undergoes an exceptional degree of character development during the course of Diamond is Unbreakable, becoming more assertive throughout many confrontations with evil Stand users. His greatest leaps are illustrated by the metamorphosis of his Stand, Echoes.

One of Koichi's constant trait is his friendliness. Koichi is a nice person, acting polite toward any stranger and acquaintance, and being happy to help. That friendliness is regularly exploited by Rohan Kishibe to have someone to hang out with. Having a gentle heart, Koichi usually doesn't seek to harm his opponents, notably having saved Yukako from death even though she wanted to kill him before and briefly fighting Giorno Giovanna without the strength to kill, which saved him. However Koichi's friendliness disappears on the rare occasions he is angered, and he becomes more abrasive, violent and vulgar. Koichi also possesses a rather cheerful personality. He finds wonder in the most various facts (his new bike, a famous mangaka living in town, finding an error in a map...), and has little trouble befriending people.

Another one of Koichi's primary characteristics is his courage and associated virtuousness. Heaven's Door exposes Koichi as a cowardly but courageous youth when push comes to shove. True to that assertion, Koichi is very prone to express anxiety, fear and despair at various setbacks, but still soldiers on and braves danger. He takes an active role in the hunt for evil Stand users in Morioh unlike Josuke, being concerned after his encounter with Tamami Kobayashi about what Stand users can do to his family and prioritizes chasing the enemy, which once backfired against Sheer Heart Attack. Initially weak-willed, acquiring a Stand and fighting others made him more confident in himself and assertive, going from being bullied by upperclassmen to facing down and taunting Yoshikage Kira while on the verge of death. By Vento Aureo, Koichi has grown into a totally confident youth.

The mix of these two traits make Koichi an extremely likeable individual, earning the friendship and respect of the vast majority of the cast including Josuke Higashikata, Tamami Kobayashi, Toshikazu Hazamada, Rohan Kishibe, Yukako Yamagushi, Aya Tsuji and Jotaro Kujo.

Koichi is a relatively perceptive individual, able to make quick and decisive moves in a fight, sometimes at the cost of being too imprudent. For the most part, Koichi tries to analyze his situation before acting, notably due to how weak his Stand is at the start of the series and the severe limitations of his powers, but regularly oversees a critical consequence of his actions.

After a difficult start in his relationship with Yukako, due to her kidnapping Koichi, he eventually fell in love with Yukako's tough and unforgiving personality. His love was such that he was willing to be blinded forever in case Yukako became ugly, so as to ease her pain.

Terunosuke states that when Koichi is scared he blinks twice. In addition, Koichi mentions during the Atom Heart Father arc that he has claustrophobia.

Abilities
Koichi's Stand, Echoes, starts off with ACT1 only. As Part Four progressed, Echoes evolves, giving Koichi new abilities to use. By the end of Part Four, Echoes gains ACT2 and ACT3. He is able to willingly call upon Echoes' previous ACT forms at will and utilize their unique abilities.

ACT1 enables him to write on any surface, causing the words or onomatopoeia to continuously repeat at various volumes.

ACT2 enables him to write a sound effect on any surface. If the word is touched, a special effect related to the sound effect is activated.

ACT3, a humanoid Stand, facilitates conventional melee attack and the ability to "freeze" targets by ascribing them unbearable weight.

Jotaro Kujo! Meets Josuke Higashikata
Koichi is a first-year student in class 1-B of Budogaoka Highschool. At first, meets Josuke Higashikata after he defeats delinquents and seems to fit the "best friend" spot.

The Nijimura Brothers
Koichi is shot with the Bow and Arrow by Keicho Nijimura, who was searching for a Stand capable of killing his father. Koichi then developed the egg-shaped Stand Echoes, whose ability was still unknown. Koichi tried to help defeat Keicho, but couldn't control his Stand.

Koichi Hirose (Echoes)
Koichi remains well-involved with the overall plot, his Stand even evolving multiple times as he fights a few battles on his own. He is victim of the con artist Tamami Kobayashi, who threatens his family in exchange of money. In this battle Koichi develops Echoes ACT1 and defeats Tamami, who later befriends him.

Toshikazu Hazamada (Surface)
With the help of Tamami, Koichi finds the Stand user Toshikazu Hazamada and is quickly defeated, but still befriends him too.

Yukako Yamagishi Is in Love
Yukako, a fellow student in love with him, at first proved to be very difficult for him to deal with as she was very aggressive in her affections towards him. Koichi tried to look like a "bad guy" to keep her away but this plan backfires as she goes to the point of kidnapping him and threatening his life should he not appreciate her efforts to "change him into a better person". Koichi defeats her in battle after developing Echoes ACT2, but saves her life in the end.

Red Hot Chili Pepper
Akira Otoishi reveals later that Koichi was one of the Stand users he watched with his Red Hot Chili Pepper.

Let's Go Play at the Mangaka's House
Alongside Toshikazu, Koichi goes to the house of famous mangaka Rohan Kishibe to ask for an autograph. Even though Koichi gets scared by his actions to make his manga look realistic (like cutting open a living spider to see its insides), Koichi and Toshikazu sneak into his office to see his original drawings and are affected by Heaven's Door as a result. Rohan plans to use Koichi as a character for his manga, ripping pages of him every day. He is saved by Okuyasu and Josuke, who defeats Rohan after having his hair insulted. Rohan also ends up befriending Koichi.

Rohan Kishibe's Adventure
Rohan and Koichi accidentally find Reimi Sugimoto's alley and learn about the killer Yoshikage Kira.

Yukako Yamagishi Dreams of Cinderella
When Yukako searches for Aya Tsuji's help, Koichi is beginning to be attracted to Yukako. He even offers to become blind in case he fails to help Yukako return to her old appearance (changed by Cinderella). Later in the story, still lovestruck, she seemed to have learned from her mistakes in trying to force him and approached him more carefully, upon which Koichi warmed up to her and slowly, willingly, became her boyfriend.

Sheer Heart Attack
With Jotaro Kujo, Koichi finally encounters the killer Yoshikage Kira and develops Echoes ACT3. He gains a lot of credit in the battle, as his courage is fundamental to keep them alive from Killer Queen's Sheer Heart Attack ability. He was nearly killed before Jotaro was able to immobilize Kira.

Atom Heart Father
Later, Koichi, along with Josuke, Okuyasu and Jotaro search Kira's house, but the group is attacked by Kira's father, Yoshihiro.

Highway Star
During Josuke's encounter with Highway Star, Koichi helps locate Yuya Fungami by tracking his Stand.

Enigma Boy
Koichi is kidnapped by Terunosuke Miyamoto, whom traps him in a piece a paper with his Stand, Enigma. His life is put into danger when Terunosuke throws Koichi in front of a car, but he ends up being saved by Yuya.

Cheap Trick
Koichi also tries to save Rohan from Cheap Trick, but almost rips out Rohan's back in the process.

Crazy Diamond Is Unbreakable
Koichi finally finds Yoshikage Kira again and is fundamental to his defeat, as he freezes Kira's finger before he could activate his Bites the Dust ability. After Kira's death, he then sees off Reimi as she, along with her dog goes to heaven.

(The information below derives from the TV Anime. As such, it may or may not be considered canon.)

He is seen hanging out with Yukako next to the Angelo rock and wants to eat a lunch she made and holds her hand as they walk. He is later seen talking to Josuke and Okuyasu about a rumor the latter heard about Rohan being caught shoplifting at Kame Yu.

The Book: 4th Another Day
The information below derives from a Light Novel not written by Araki. As such, it may or may not be considered canon.

After the events of Part 4, Koichi and Rohan find a cat (named Trinita) covered in blood and the two try to find his master. Koichi soon discovers that Hanae Orikasa, the cat's master, was killed under mysterious circumstances and tags along with Rohan to find the killer. After taking Trinita from the police station via Echoes, they discover, with the help of Heaven's Door, that the killer might be a Stand user, and has a very distinct characteristic: red marks on his arms.

Koichi later works with Yukako to discover if the killer is from the same class as them, using his Echoes ACT2. Learning the fact that there are multiple students in the school with this feature, Koichi tries figuring out the secret inside this. After Koichi knows about Josuke's mother Tomoko getting attacked, he meets up one of his schoolmates with red marks on his arms, asks him about this, and gets surprised with his response that he actually did this by himself. Then Rohan comes and uses Heaven's Door to read the schoolmate's memory. By reading his memory, Rohan deducts the Stand ability of the culprit, and erases those madeup memories. After this investigation, Koichi asks Rohan to erase the memories from Tomoko as well.

Later, in March, 2000, with Rohan's investigation, Koichi and his fellows have more information about Hanae Orikasa and the culprit. When Koichi and Yukako are studying at Thorn Parlour (Morioh public library), they encounter Chiho Futaba. Koichi is a little confused to know that Chiho knows his name.

On a snowy day, Koichi goes home by bus after school and runs into Josuke. They talk a little about the pompadour young man who saved Josuke's life when he was 4. Then Koichi glances a slide. They run to the spot and find an orphenage. After they ask the staff and the dean, Josuke and Koichi are quite sure that Takuma Hasumi is the culprit they are chasing. After getting Takuma's address, Koichi and Josuke decide to go to his home next day.

That night, Koichi is informed by Yukako that Chiho's home is on fire, so he immediately calls Josuke, who doesn't reply and is actually on his way to Takuma's home. Josuke calls back when he fails to find Takuma in his home, then Koichi tells Josuke that Takuma might be at Thorn Palace now. Finishing the phome call, Koichi starts walking to Thorn Palour. Koichi also calls Okuyasu and tells him to go to Thorn Parlour on his way. It's assumed that the battle between Josuke and Takuma is already over when Koichi eventually arrives Thorn Palour, and Koichi calls the ambulance and police anonymously.

In August, 2000, Koichi comes across Chiho accidentally, who is now living with her mom outside Morioh. After some chatting, he is astonished to find out Chiho is pregnant with Takuma, her half brother's child. Deciding to keep this encouter as a secret, Koichi prays that Chiho and her child will have a good future when Chiho is leaving Morioh.

Rohan at the Louvre
Koichi makes a brief appearance, hearing Rohan's story about Nanase Kishibe along with Okuyasu and Josuke. Koichi questions Okuyasu about his opinion on Rohan's likeness with Mona Lisa, as they have different genders.

Gold Experience
Jotaro sends Koichi to Naples, Italy to locate Haruno Shiobana in order to get a skin sample for the Speedwagon Foundation to test, having asked Rohan to write 'Italian language skills' into him with Heaven's Door to make the ordeal easier. Shortly after arriving, Koichi notices Giorno performing in the street and then subtly bribing the policemen watching. Giorno offers to give him a ride, but Koichi refuses until noticing the long line of people waiting for a taxi. Unfortunately, the offer was a trick and Giorno starts to drive off with Koichi's luggage before he can get in the car. Using Echoes ACT3, Koichi stops the car but Giorno simply smiles and flees the scene after transforming the luggage it into a frog. Koichi overhears the nearby policemen talking about Giorno's failure and realizes that "Giorno Giovanna" is actually the "Haruno Shiobana" he'd been sent to find. He doesn't, however, figure out that the frog he found in the back of the car is actually his luggage.

Gang Enrollment
Some time later, when Giorno is undergoing the test to join Passione, Koichi locates his apartment and searches for his missing luggage. He nearly extinguishes the lighter flame which Giorno had stood in a loaf of bread, but Giorno whisks it away with Gold Experience just in time. Having successfully found his passport, Koichi leaves the apartment building only to stumble upon Giorno and a dead janitor. At first he believes Giorno is responsible, but soon learns that it was Black Sabbath's doing. He ends up helping Giorno to defeat the Stand, noticing in the process that it possesses part of the Bow and Arrow. Koichi then accesses a payphone to inform Jotaro, but Giorno stops him and Koichi decides to remain quiet in deference to Giorno's virtuousness and behavioral similarity to those of the Joestar bloodline. Afterwards, Koichi heads on home since Jotaro calls off the search as his prediction was correct.

Allies

 * Josuke Higashikata: One of Koichi's main best friends, the two quickly got along the first moment they met. Koichi admires Josuke and looks up to him while considering him a kind strong person. In turn Josuke also relies on Koichi during battles and is impressed by his bravery. Josuke is willing to help him whenever he can, such as when Yukako goes after Koichi.
 * Okuyasu Nijimura: The two met on bad terms as Okuyasu slammed some doors between Koichi's neck nearly choking him. However, they moved on from that and became friends. While Koichi and Okuyasu do not have much interaction, they've shown to care for each other's well-being. Okuyasu was concerned when Koichi was kidnapped by Yukako and during the Red Hot Chili Pepper arc, Koichi was sympathetic and comforting to Okuyasu's plight and desire for vengeance against Red Hot Chili Pepper. Nonetheless, Okuyasu is mildly jealous of Koichi's relationship with Yukako, as Okuyasu himself hasn't had a girlfriend.
 * Jotaro Kujo: Koichi looks up to Jotaro as a strong ally, although he is put off by Jotaro's aloof temperament. Their cooperation during the Sheer Heart Attack story arc had Jotaro act as a mentor figure to Koichi, who came to really respect Jotaro's prowess in battle. In addition, Jotaro also grows to see Koichi as a good friend and a reliable person, enough so that he chose him to go to Italy and investigate Giorno Giovanna.
 * Rohan Kishibe: Koichi first admired Rohan as a talented mangaka, but his view changed quickly upon their first meeting when he and Toshikazu Hazamada went to visit Rohan. While Rohan liked Koichi and grew to see Koichi as his first (and possibly only) true friend, he was still abrasive and pushy, notably pressuring him to accompany him on two occasions, and Koichi tolerated less and less the worst sides of Rohan's arrogance as he gained confidence and he was overall a positive influence on Rohan's attitude. At the end of Diamond is Unbreakable, one reproachful look from Koichi was enough for Rohan to yield and confess an attachment to Reimi Sugimoto.
 * Yukako Yamagishi: When Yukako first confessed her feelings to him, Koichi was happy but quickly lost interest upon learning of her obsessive personality, made worse when she kidnapped him. He managed to defeat her and remained somewhat frightened of her. However, during the Cinderella arc, Koichi sought to reconcile with her and grew attracted to her forceful and aggressive personality, ultimately the two became a couple. Koichi's affection for Yukako was such that he was willing to blind himself if Yukako ended up being ugly due to Cinderella's power in order to ease her pain.
 * Reimi Sugimoto: The two met when he and Rohan stumbled upon the haunted alleyway she resided in. While initially scared upon hearing she was a ghost, he quickly sympathized with her after hearing her tragic story and promised to find her killer so she may rest in peace. He later bids her farewell when she ascends to heaven, and was rather saddened with her parting. He also gave Rohan a reproachful look so he would admit he would miss Reimi too.
 * Tamami Kobayashi: Initially Tamami tried to scam Koichi with his stand, but Josuke and Okuyasu intervened. When Tamami tried to involve Koichi's family, Koichi got so angered he awakened his Stand and beat Tamami. Since then, Tamami has become afraid of Koichi but also genuinely respects him. Their relationship has been described as a one-sided boss-subordinate relationship.
 * Toshikazu Hazamada: Koichi and Josuke fought him and quickly defeated him. Afterwards, Hazamada somewhat bonded with Koichi over their mutual interest in Pink Dark Boy and the two went to visit Rohan's place. Their relationship has been described as a one-sided friendship.
 * Aya Tsuji: While the two had little interaction, Aya grew to respect Koichi's determination when she saw his willingness to blind himself if he couldn't help Yukako through the trial Aya put her through. He was also saddened when Kira killed her.
 * Family: While not much interaction was shown with his family (which consists of his parents and older sister), when Tamami tried to use them to get revenge on Koichi, he became enraged enough to beat Tamami by awakening his Echoes ACT1 Stand, demonstrating that he cared for them. His relationship with his father is never shown but is presumed to be good.
 * Giorno Giovanna: Koichi was sent to investigate Giorno by Jotaro, and Giorno did his best to avoid Koichi even turning his suitcase into a frog. However, over time Koichi grew to see Giorno's noble soul and was conflicted on whether to report him to Jotaro, but decides not to as respect to Giorno.

The Book: JoJo's Bizarre Adventure 4th Another Day

 * Chiho Futaba: Koichi firstly meets Chiho in Thorn Palour while studying with Yukako, and gets to know her through Yukako's introduction. He runs into Chiho again about 5 months after Takuma Hasumi's case. Surprised to find out that Chiho is pregnant with Takuma's baby, Koichi decides to keep this encounter as a secret and sees Chiho leaving Morioh, sending his wishes to her.
 * Takuma Hasumi: After discovering Trinita and Hanae Orikasa's corpse, Koichi and Rohan starts investigating to find the culprit, who is ensured to be a Stand user. Later, Koichi runs into Takuma at the hallway in his high school, along with Josuke and Okuyasu, without realizing Takuma is the culprit and has already sensed their actions.

Enemies

 * Yoshikage Kira: Koichi, after learning of Kira's crimes, came to deeply loathe him to the point he would attack him on sight. Kira, on the other hand, came to somewhat praise Koichi's ability for being able to track him and then indirectly humiliate him in public, which he made sure to pay back with a beating. When Koichi humiliated Kira a second time, demonstrating how careless the serial-killer could be, Kira was enraged and came to detest Koichi, being happy at the prospect of Koichi dying.
 * Terunosuke Miyamoto: While there is little interaction between the two, Koichi hated Terunosuke for taking him hostage and trying to kill him and Josuke.

Vento Aureo (PS2)
Koichi was planned to be in the GioGio PS2 game, likely as a playable character as there are beta pictures of him appearing in the game (such as one of him appearing with the main characters of Part 5 and in another one looking for Giorno and his stolen luggage). However, for unknown reasons Koichi was removed from the game, with no trace of him even in the game's Gallery Mode (unlike other characters, such as Risotto Nero or Leaky-Eye Luca, who do not appear in Story Mode but have viewable characters models regardless).

In canon Part 5, Koichi has a confrontation with Giorno over his stolen items and later helps him fight against Black Sabbath. As he was absent from the game, the Story Mode begins with the narrative skipping to Giorno on the tram being confronted by Bucciarati in Chapter 1, and in Chapter 3, Giorno fights Black Sabbath by himself.

All-Star Battle (PS3)
Koichi makes his playable debut in the PS3 game, and was confirmed along with Akira Otoshi. Koichi is voiced by Romi Park, who previously voiced both Giorno Giovanna and Gold Experience Requiem in the aforementioned PS2 GioGio game, coincidentally.

Along with Enrico Pucci, Kosaku-Kira, Johnny Joestar, Hol Horse, and Giorno Giovanna, Koichi is a character who can utilize more than one Stand during a match as part of his moveset. In gameplay, Koichi uses all three forms of Echoes as part of his moveset, unlike Johnny or Pucci, who need to evolve their Stands during combat.

As one of the mass majority of playable characters in the game with the "Stand" Style, Koichi can turn Echoes ACT3 on/off, changing movesets, as well as having access to the Stand Rush ability returning from the Capcom game, being able to attack in conjunction with his Stand.

During a fight, Koichi can use several different abilities that were featured in Diamond Is Unbreakable. While Echoes ACT3 is off: While Echoes ACT3 is on: Koichi's HHA, GHA, or "S-H-I-T" inflicts 3 Freeze. The opponent is made heavier as a result of ACT3. This results in them moving much slower and being unable to jump for a period of time, forced into a constant crouch. While the effect cannot be broken by hitting Koichi or gaining enough distance, it has a relatively short duration, slightly altered based on the attack that generated it.
 * Throw - Whooooosh!: ACT2 hits the opponent with a "Whooosh!" SFX, sending them flying.
 * Enough!: Koichi runs forward and swings with all his might. If the punch connects, the opponent is sent flying upon impact. Koichi's skills can be performed instantly following this move. (Comboable)
 * I'll never forgive you!: Koichi summons ACT1 to fly forward and assault the opponent with loud SFX. This move has a follow-up. (Comboable through Puttsun Cancel)
 * Cicada's cry etched in stone: ACT1 increases the number and volume of SFX to the point where the opponent collapses. (Comboable)
 * Sizzle!: ACT2 throws its tail end in an SFX that arcs. If it hits the opponent, they will catch fire and gradually lose health over time for a few seconds. This move doubles as an anti-air. (Comboable through Puttsun Cancel)
 * Kaboom!: A counter. Koichi crosses his arms and glares, and if the opponent hits him during that moment, SFX by ACT2 will reveal itself on Koichi and they will be blown back.
 * Boing!: ACT2 slaps an SFX on the ground in front of Koichi. If the opponent comes in contact with it, they'll be blown upward into the air and take slight damage upon landing (Comboable). If Koichi himself touches it, he will leap high into the air, allowing him to evade many of the opponent's attacks or set up his own attacks from the air.
 * Hit them, ACT3!: ACT3 flies forward, rapidly punching the opponent and pushing them away. (Comboable through Puttsun Cancel)
 * S-H-I-T: ACT3 flies into the air and comes down punching with the 3 Freeze effect active, downing the opponent. This move doubles as an anti-air, and inflicts the 3 Freeze effect for a short duration. A Stand Rush skill that Koichi can disconnect from to attack the opponent while it is executing. (Comboable through Puttsun Cancel)
 * This air pressure?!: ACT3 swiftly moves in front of Koichi and unleashes an intense burst of air capable of knocking both him and the opponent back. This skill can interrupt an opponent's combo, and unlike other skills of similar effect, does not spend any amount of the HHG. However, Koichi is harmed as well for even more damage. Koichi may recover up to half of the lost health over time, but only if he does not receive any more damage during the process.

Koichi's HHA, "Echoes ACT3: FREEZE!!", sends ACT3 flying forward, rapidly punching the enemy with the Freeze effect active and pushing them away for an extended period of time, with the final hit knocking them down. The HHA does not require an initial hit to connect in order to work, and will not stop until it finishes or Koichi is interrupted. The HHA inflicts the 3 Freeze effect for a medium-length period of time.

Koichi's GHA, "I'm really getting stronger?!", starts with him summoning ACT1 to throw a "BAM!" SFX. If it lands, the opponent is assaulted by SFX loudly repeating itself enough to make them cover their ears. ACT2 flies in and places a "KaBOOM!" SFX under them, blasting them high into the air. The GHA finishes with ACT3 appearing above the opponent and performing a barrage of punches while activating 3 Freeze, making the opponent smash into the ground on landing. The GHA inflicts the 3 Freeze effect for a long period of time.

Aside from being a playable character, Koichi also appears on the stage "Kira Estate" as a background character along with Okuyasu. This is assuming Koichi himself is not one of the two fighters. Koichi also appears as the auto-save icon, with his face under the effects Heaven's Door as the pages flip.

Aside from the entire Part 4 cast, Koichi possesses special dialogue before a fight with Jotaro or Giorno, telling the latter that he wants his suitcase luggage back, recreating their antagonistic dynamic during early Part 5 before they leave on good terms.

Koichi also won the first place in his League Group in the All-Star Battle League, beating fan favorites such as Giorno, Jolyne, and Gyro. And even managed to reach to the semi-finals matches, but ultimately lost to Jotaro.

Koichi also possesses two alternate costumes, the first being the pajamas he wore during Yukako's introductory arc and his second one being his T-Shirt with the LUCKY.CO logo on it that he wore during his assistance in Josuke's battle against Highway Star.

Eyes of Heaven (PS3/PS4)
Koichi was confirmed for the game alongside Yukako.

Once again Koichi is voiced by Romi Park and his main color scheme is the same from the previous game.

In the post-credit of the new JoJo timeline where most of the fallen allies (including the actual Kosaku) are now alive well, including Joshu's relationship Part 8 Josuke becomes very well, during the retelling story of the Part 4's first chapter where he met Jotaro, Koichi is having a deja vu that he met a younger Jotaro somewhere before.

Tournament
He is paired with Will A. Zeppeli in the Eyes of Heaven Tournament, but was eliminated in the preliminaries by Jonathan Joestar and DIO.

Gallery
Manga=

Trivia

 * Koichi's name and basic appearance appear to have been taken from the narrator of Chapter 1 of one of Araki's earlier works, Gorgeous Irene.
 * Koichi's surname, "Hirose," is derived from the Hirose River (広瀬川), located within the city of Sendai, Araki's birthplace.
 * Although it's never been explained why, Koichi's enemies tend to shrink in size after he beats them. This is not shown in the anime for consistency; Koichi's enemies are already short when they're introduced.