Samatarou is not just an average high-school boy, the truth is that he is the son of a god, his mother is a goddess and his sisters are candidates to become goddesses. They are living in the human world, because they want their boy to learn about the human customs and the habits of the creatures that they are protecting, so that in this way Samatarou will become a better god. Tenko is a angel assigned to look after Samatarou. (myanimelist.net)