Tsukasa Tenma is a time traveler who must explore different universes and timelines and correct some "anomalies" that are ruining the outcome of the universe. He is not completely human, he has no need for food, sleep, drink, etc. He lives in an empty space where everything is surrounded by hourglasses and columns, but most often Tsukasa hangs around with Rui and in other worlds. Tsukasa tries to help other universes, but most often it has dire consequences that Rui has to correct.