Yoshikage Kira

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

Story
Kira (which sounds similar to Killer in Japanese) longs for a simple life, and doesn't wish to be bothered. Although he reveals many talents, this yearning shows in his dislike of coming in first, as the cast eventually realizes. He becomes quite bothered when someone disrupts his "simplicity", and goes to extreme lengths to get it back. Kira also has a bizarre fetish for the female hand, stemming from an erotic fascination with the hands of the Mona Lisa. Unfortunately, his desire has never extended to the rest of the female person. This results in his 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). However, his Stand, Killer Queen, eventually awoke from his desire to leave no evidence behind of his killings--hence its ability to make its victims completely disintegrate. He now lets Killer Queen annihilate his victims (except for his "girlfriends"-hands), letting everyone else think that the victims have simply gone missing. Even if the number of missing attracts attention (as it eventually does), no one would have any reason to suspect that Kira was involved.

When Josuke and his friends pursue him for his crimes he is forced to go into hiding by assuming the identity (with the help of the Cinderella stand) of Kosaku Kawajiri – husband of Shinobu Kawajiri and father of Hayato.

Even after being killed by Star Platinum and Echoes Act 3, Kira is somehow existing as a spirit who doesn't know who he is and is just a vagabond (between the end of Part 4 and the End of Part Six).

Stand
Killer Queen

Under Jailbreak, Under Excecution
One of the short stories compiled in the Under Jailbreak, Under Excecution oneshot features Kira and what had happened to him after his death.

Trivia

 * Killer Queen's first onscreen victim is Fatty.
 * Favorite fashion brand is Gianfranco Ferré and favorite movie The Remains of the Day.
 * When on a normal date, all he can think about is how much he wants to go home.
 * Graduated from University D's literary faculty.
 * He won several awards, making it a point to never rank better than 3rd in any competition in order to not stand out. He won: 3rd place in primary school essay contests, 3rd place in the school track and field championship, 3rd place at the 200-meter hurdles, and 3rd place at high school music competitions (violin).
 * Every 4 to 5 years when his nails grow really fast, he gets aware of his powerlessness to resist his urges. During the crime he interviews the female about her likings, name and hobbies etc but he hates when they talk on their own accord about personal things. He takes her hand back home to play with it - after taking a dump, it's the greatest bliss for him to have that hand help him wipe his ass.
 * It is his hobby since 1975 to collect his victims' nail clippings, keeping track of their statistics and length.