He is one of Bishamonten's Shinki and her most trusted person. His shape as a Shinki is a flower-shaped earring, and is capable of tracking enemies. He has some kind of debt towards Yato, calling him his benefactor. Kazuma is the only Bishamonten's Shinki with "ma" on his name, while other of her Shinkis have "ha" on their name since Kazuma is the only Bishamonten's Shinki who survived on a massacre that Yato caused.
SpoilerHe is the last survivor of Bishamonten's old Shinkis, who were killed by Yato, because they were occupied from demons. He asked Yato for killing Bishamonten's old Shinkis without knowing her to save her.