The primary antagonist of the series. He’s an intersex person, possessing qualities of both an angel and an immortal, which, according to him, makes him a “god”. He seems to have no concept of human morals but instead, has a sadistic sense of amusement and beauty.
Apos is revealed to be the child of Tajimamori, the previous Guardian of Yggdrasil, and the current Guardian himself. Guardians are supposed to switch every once in a (long) while, but Apos desires to become a permanent guardian by sacrificing Rin to Yggdrasil.