Yuinka ends up having a relationship with her best friend Risa's boyfriend after an unexpected encounter. Although she thinks it's not a good idea, she sees Risa's disheveled and drowned appearance and seeks the same encouragement and continues the relationship.... A test with Risa . Studying While Risa prepares tea, Yuinka straddles her boyfriend and buries her. She is a beautiful obscene girl who indulges and devours her boyfriend, who is the complete opposite of her distaste for men. Yuinka feels more guilty than Risa. Indecent... carnal desire.... In such a situation, Risa, her boyfriend and Yuinka plan a trip to the hot spring....