Although Takaki is an ordinary high school student, his family is quite strange. His parents are former heroes, and they now regularly adopt young girls with unusual abilities—mediums, aliens, or girls coming from another world. Nothing is too weird or crazy for Takaki’s family. He gets used to this lifestyle, and he gets along very well with each of his adorable sisters.

But one day, his number of sisters increases once more. And the newcomer seems even stranger than the others: the young girl in question comes straight from the future!