Nagi Umino and Erika Amano face new challenges as they navigate their unusual domestic situation, sharing a home with Nagi's sister Sachi and Hiro Segawa. Their lives become even more complicated with the return of Nagi's childhood friend Ai Mochizuki, who announces her intention to marry him despite his rejection. Ai remains committed to having Nagi to herself, adding to the complex dynamics with Erika, Sachi, and the other girls who have their own thoughts about him. This situation forces Nagi to reevaluate his feelings and consider the most suitable path forward.