High schooler Yūta Iridatsu has experienced “astral projection” i.e. his spirit has been separated from his body. To only have woken up in a mansion named Koraikan. Where he meets a cat spirit named Chiranosuke; which tell him “You must find the Sacred Tome of Koraikan in order to return to your physical body.” While searching through corridors of Koraikan. Yūta bumps into the underpants of its female residents, and by doing so would, eh, create some big trouble for planet Earth.