He was once a middle schooler with a passion for reading and especially for Shinobu Akiyama's books. He got killed by a crazy gunman while protecting a girl (who he didn't know, named Shinobu Akiyama) in a cafe robbery. Regretting to unable to read Shinobu Akiyama's latest novel and having the desire to live, he was resurrected as a dachshund much to his surprise.

Kirihime would refer to him as: Mongrel, Mutt or Dog, but it was Yayoi who gave him the name "Kuro."

(Source: Animefreak forums)