Fuyunosuke is a college student living in Tokyo. One day, he is visited by what appears to be an extraterrestrial being. He calls the strange-looking creature "brother". Yes, the two of them are real brothers and aliens from outer space. Fuyunosuke gives him the name Natsutaro, and they begin living together. Their purpose is to survey the planet's suitability for the activation of the Earth Migration Plan, and Fuyuosuke is imposed with
