Yoshikage Kira

Yoshikage Kira (吉良吉影, Kira Yoshikage) is the main antagonist of Part IV: Diamond is Unbreakable.

Personality
Kira longs for a simple life and does not wish for it to be interrupted. Although he reveals many talents, this yearning shows in his dislike of coming in first, and he even made it a point to never rank better than 3rd in any competition so as not to stand out. He even pulls this streak of third places quite easily, winning 3rd place in primary school essay contests, the school track and field championship, the 200-meter hurdles, and high school music competitions (violin). He becomes bothered when someone disrupts his "simplicity" and goes to extreme lengths to get it back.

However, beneath his facade of simplicity, Kira is very abnormal. The most abnormal characteristic of Kira his fetish for the female hand, stemming from an erotic fascination with the hands of the Mona Lisa. However, his desire has never extended to the rest of the female person; in fact, when on a normal date, all he could think about was how much he wanted to go home. This results in murdering women in order to acquire their (severed) hands as "girlfriends"; when one "girlfriend" begins to decay, he goes off in search of a replacement. He measures and collects his own fingernail clippings, using them to divine his murdering luck off of their length.

Originally, Kira murdered his victims by stabbing them so viciously they were left with horrific back wounds (their hideous nature is implied by the fact that the reader is never actually shown Reimi's wound despite all the instances of blood and gore that Araki had drawn up to that point). However, his stand, Killer Queen, eventually awoke from his desire to leave no evidence behind of his killings and developed an ability to make its victims disintegrate completely. He now lets Killer Queen annihilate his victims (except for his "girlfriends'" hands), letting everyone else think that the victims have simply gone missing. Though the number of missing people would eventually attract attention, no one would have any reason to suspect that Kira was involved due to his simplicity.

Diamond is Unbreakable
Kira is first seen holding the severed hand of another woman, later placing it inside a sandwich bag for later. However, Shigekiyo "Fatty" Yangu orders a sandwich from the same shop, and unbeknownst to Kira, accidentally swaps it with his sandwich bag, forcing Kira to retrieve it out of fear that he might be discovered. After Kira retrieves it, however, Fatty becomes enraged that Kira had stolen his sandwich bag and demands it back, only to become the first victim of Killer Queen and literally erased from existence with its explosive abilities. However, Killer Queen failed to erase one of Kira's buttons, which one of Fatty's Harvest brings to Josuke and Okuyasu. Josuke and company eventually deduce that Fatty was somehow killed and back each other in defense against Fatty's killer.

Later, when Kira turns in his suit to be fixed and finds that Jotaro Kujo and Koichi Hirose are investigating him, he sets off Killer Queen's Bomb No. 2: Sheer Heart Attack against them and successfully wounds Jotaro. Koichi, however, awakens Echoes Act 3 and traps Sheer Heart Attack in place, transferring the effect onto Kira himself as he finds his identity in jeopardy. Kira then returns in person and, heavily wounded, cuts off his own hand in order to let Sheer Heart Attack loose. Josuke and company pursue him and Kira is forced to go into hiding by assuming, with the unwilling help of Aya Tsuji and her stand Cinderella, the identity of Kosaku Kawajiri, successfully stalling the protagonists' chase for a long time.

Once found out that he was taking another identity, Josuke and the gang began the pursuit only to be trapped in a time loop made by Kira's stand (which repeatedly results in Rohan's and their deaths, among other things). However, Hayato manages to take advantage of the time loop and cause Kira to eventually cancel the loop and expose himself by gloating about his victory despite Hayato's efforts. Josuke and Okuyasu, who were walking down the street nearby, notice immediately and engage Kira in a fight.

Kira proves to be a difficult adversary, as he combines Stray Cat's aerokinesis with Killer Queen's explosive charges to produce invisible air bombs that make his fight with Josuke and Okuyasu difficult. After defeating Okuyasu, Kira charges Okuyasu's body to explode on contact, forcing Josuke into a dilemma over whether to take a chance at healing Okuyasu or to pummel Kira. Hayato, however, jumps in the way and sets off Okuyasu's bomb himself, after which Josuke pieces the two back together with Crazy Diamond and resumes his fight with Kira.

Despite the impediment, Kira refuses to back down and his air bombs retain their accuracy even after Josuke attempts to escape them. Hayato eventually finds out that Yoshihiro had been hiding in his jacket pocket and had been giving instructions to his son and Josuke deprives Kira of his means to attack them accurately by faking the radio call and directing an air bomb to incinerate Yoshihiro's photograph. Without the accurate means to incinerate Josuke any further, and with Josuke's blood still on his shirt, Kira is defeated when glass shards stained with Josuke's blood strike him via Crazy Diamond's restoration abilities.

Kira, unwilling to accept defeat, is pummeled out into the neighborhood sidewalk, exposed to the crowd of people he did not want to get noticed by. Unwilling to accept this irony, Kira attempts to use Another One Bites the Dust again and escape.

However, Reimi reveals that Kira had been delusional, and that his attempt to activate AOBtD had actually been foiled by Echoes Act 3's "freeze" technique. Jotaro, who had finally gotten close enough, beats Kira with Star Platinum's barrage. Kira, still alive, but unable to activate AOBtD with broken fingers, is finally and accidentally crushed by a nearby ambulance.

Upon recognizing Reimi and wondering why she would show him her back wound, Kira recalls that his father told him about a place he could not turn his back to when he died, lest he be dragged to another world, and attempts to force Reimi to look back instead. However, even this plan manages to fail when Arnold bites his hand off. Kira falls to the ground, ends up turning around in surprise, and is torn to pieces and dragged off to another world by a swarm of hands.

Under Execution Under Jailbreak
Kira is shown some time between the End of Part 4 to the End of Part 6 as a vagabond spirit who is unaware of his identity. Dead Man's Questions, one of the short stories compiled in the Under Execution Under Jailbreak one-shot, features Kira and what had happened to him after his death.

Part VIII: JoJoLion
Kira's counterpart in the alternate universe is a marine doctor who appears to be just as twisted as the original, beliving in definite qualities, having an obsession with the human hand, and convincing Sasame Ojirou to eat his fingers for being indecisive about "being a man of the sea or a man of the land". Of note is that the protagonist of JoJoLion also suffers from amnesia and was initially suspected to have been named "Yoshikage Kira" and holds a 95.8% DNA match with Kira of the alternate universe, who is revealed to have been the son of Yoshiteru Kira and Holly J. Joestar.

Trivia

 * His character was probably inspired by Tom Lehrer's song "I Hold Your Hand in Mine".
 * Kira's favorite fashion brand is Gianfranco Ferré.
 * Kira graduated from University D's literary faculty.