Coming with My Brother! [お姉ちゃん、弟といく]

Morishita Nao (Eguchi Noriko) shares an apartment with a female friend. Her roommate's younger brother Kotaro (Nakamura Kuniaki) leaves their family home and comes to stay with them. That evening, Nao witnesses Kotaro smelling her panties. The next day Nao begins acting provocatively towards him.