A seemingly "normal" office worker Hiroko has a secret. At home she lives with a prosthetic torso - no head, arms or feet, just body and penis. Hiroko bathes with the torso and she also makes love with the torso at night. Hiroko's secret life is interrupted when her outgoing sister Mina rings her doorbell. Mina is running away from her abusive boyfriend and wants to stay at Hiroko's home.