Kiriya is the chief of the Police Department Special Squad, overseeing the six young men and women who fights against the threat of ghosts. He is a master of swordsmanship.
During the Bakumatsu era, he was a ronin traveling throughout Japan, helping out people he encountered. Many of the important figures in the new government are people he had helped during his travels, which is how he got recruited for the job.
His true identity is, in fact, Izanagi.