One day, university student Narumi Daisuke meets a pink kigurumi rabbit in the street. This kigurumi, named Arita, falls in love at first sight Daisuke! But, no matter where the two meet, it seems that Arita won't take off his bodysuit. To Daisuke, who finds this strange, Arita makes a shocking confession! If he takes off his costume, he will die... "The truth is, I'm an Undergrounder!" Is he for real?!