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. He keeps a collection of his own fingernail clippings, and believes when they grow quickly he has trouble. 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.

He is the main antagonist of JoJo's Bizarre Adventure: Diamond is Unbreakable.

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 "girlfriend"-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.
(Source: Wikipedia)