Sumire-chan is an 18-year-old student who can't refuse her boyfriend's requests and whose anus has been "developed" by him. Despite being a hardworking third-year student in the table tennis club, her anus has expanded so much that a ping-pong ball can fit through it beyond the net. He always goes in raw. What's more, she's grown to love anal sex so much that she even squirts. With her anus now firmly established at this age, Sumire-chan's life seems destined to be that of a prostitute...