lore

It's basically a being which is neither from the death world nor human world, sometimes they slip into the world of living and attract lots of impurities(those monsters). They also can distort reality which falsely got interpreted as granting wishes by the humans. So they trapped Hikaru there thinking he was a god until Hikarus dead wished to free him and Hikaru himself wished to "not make anyone sad and leave yoshiki alone". Which is why he was able to leave in the end.