Tamami Kobayashi

Tamami Kobayashi (小林 玉美) is a character featured in Part IV: Diamond is Unbreakable. He is introduced as an antagonist of Koichi Hirose, but later becomes Koichi's friend.

Appearance/Personality
Tamami initially appears as a tall and intimidating man, but later in the story shrinks for unknown reasons, a trait shared with Toshikazu Hazamada. He has a cross-shaped scar in his cheek.

Tamami is a con artist who deceives people for money and describes himself as the "Well Known Boss Tamami". He mentions that even his parents wouldn't believe him. He hates violence, so his stand made his efforts to steal money much easier. After his defeat,  he starts working taking back loans for casinos and the mafia, apparently by making people feel guilty if they don't pay.

History
Tamami is a man who got his stand powers 4 months before the events of Diamond is Unbreakable, from Keicho Nijimura. He then intends to use his powers to gain wealth and never have to work again.

Diamond is Unbreakable
Tamami is introduced as a confidence trickster who leads Koichi Hirose to believe that he had run over Tamami's cat with his bike – supposedly hidden in a bag which then splattered with blood. Despite that odd circumstance being questioned, Tamami demands a sum of money from Koichi as a compensation for the deed. He successfully pressures Koichi into feeling guilty, which puts his stand, The Lock, into action. As its name implies it is a stand in the shape of a lock which clasps over the target's heart and grows the more guilty its captive feels.

As he is bullying Koichi, Josuke and Okuyasu turn up and try to help their friend. Okuyasu punches Tamami, breaking his teeth and as a result feels guilty for it – which gets him a lock around his heart as well. Josuke then reveals that it was just a doll instead of a cat that was hidden in the bag and heals Tamami, thus freeing Koichi and Okuyasu from their guilt and Tamami's stand.

Tamami returns the money he had taken from Koichi but vows to get revenge. When we next see him he is at Koichi's house, talking to his mother. He explains that he is there to return Koichi's wallet and claims that Koichi has intentionally switched it with his, as Tamami's holds 500,000 yen. When Koichi's mother doesn't believe him, he tells her that there is a stub of a restaurant he went to inside of the wallet Koichi holds. His words were proven true thanks to a trick, leading Koichi's mother to feel guilty about her son and giving Tamami an opportunity to place The Lock on her. Koichi, enraged, attacks him, leading in Tamami revealing he also made his sister feel guilty as well to Tamami's advantage. Tamami deceives Koichi's two family members into feeling guilty further, causing them to fall under the highest level of The Lock's power – severe enough to have them attempt suicide. Finally, Koichi manages to convice his mother that he is innocent of the crimes Tamami had framed him of, by using his stand Echoes to amplify his plea for her to believe in her own son's words. This destroys the Lock and Tamami knows he has been defeated. From then on he respects and fears Koichi and even takes to calling him Boss Koichi.

Later in the story Tamami appears to give Josuke and Koichi information on another stand user: Toshikazu Hazamada, but doesn't go investigate with them. He later encounters Toshikazu and Surface, but thinks the stand is actually Josuke (due to Surface taking his form) and is attacked by surprise. Tamami is knocked out by a brick and Toshikazu hides his body, but he ends up in the hospital by unknown means. The hit was so hard Tamami, after leaving the hospital, can't even remember what happened to him. Akira Otoishi reveals to Josuke that he has been watching Tamami with his Red Hot Chili Pepper.

Tamami briefly takes on the role as a juror when Josuke and Rohan gamble against each other during the dice game "18", instructed to use his stand on Josuke to see if he's cheating. Rohan's house catches fire before Tamami can discover Josuke and Mikitaka Hazekura's trick, but he charges Rohan for his services nonetheless. Tamami last appears to give goodbye to Reimi Sugimoto.

Mutsukabezaka
Tamami briefly appears to ask for Rohan's autograph along with Akira, saying he's a fan of Rohan's work. Both are scolded by Rohan's editor Kagamari Minoru, who tells them that Rohan is busy at the moment. However, Rohan scolds Kagamari back, saying to not threat him like slow mangakas who can't quickly sign a autograph and procceeds to use a dripping technique to sign the autographs with his own coffee.

Trivia

 * His shrinking is possibly due to him being "humbled" by Koichi, showing that he shrunk in spirit as well as size. This is evident since he never fought Koichi or anyone afterwards.