Rikka

A shinigami who's Zen's partner. Rikka is usually taciturn, though when he does talk, he's very sharp-tongued. He seldom shows his emotions, but he often quarrels with Zen. Since he completes his shinigami jobs coolly, calmly and steadily with precision, he is highly valued in the shinigami world. Rikka secretly settles the disputes Zen causes behind the latter's back. Possessing a thought process colder than everyone else, he thinks it's fine to send all spirits in the world of the living to hell.

Spoiler

His full name is Minato Rikka. He had worked as Ame's servant when he was alive. Though he was never informed of it, he had a child with Ame's sister Akari, making him Hotori's great-grandfather.