Ryosuke has an older sister, Yukina, who is always severe with him. Haruaki, Ryosuke's neighbor, also has an older sister, Youko, who is always soft with him. Ryosuke and Haruaki are friends and always complain about their older sisters. One day, their parents go abroad on vacation and they decide to swap their older sisters.... Severe older sister or soft older sister.... Which one would you choose?