The strong-willed and slightly spoiled older sister, Yuuha, and the quiet, easily pushed-around younger sister, Chiharu. The two were having tea in the living room while complaining to each other about their boyfriends. When Chiharu mentioned that her boyfriend's sex was too intense and it was bothering her, Yuuha felt a bit envious and became interested in him. So, Yuuha proposed to Chiharu, 'How about we exchange boyfriends?'
