Toshio's girlfriend Yui visits Toshio's house. Toshio's older brother Hikaru meets Yui and finds out that she is a masochist. Hikaru, who planned to train his girlfriend Yui, looks at her and treats her kindly. One day, when Toshio wasn't home, Yui came to Toshio's house to pick up something she had forgotten, and when she received tea from Hikaru, she spilled it on Hikaru's crotch.