Yuji Agatsuma finds himself in a complicated situation living with his married older sister, Aya, in Tokyo. Despite being near his university, he grapples with the challenge of hearing his sister's amorous encounters with her husband every night. As Aya blossoms into a stunning and alluring woman, Yuji wrestles with feelings of longing and loneliness, seeking comfort in the arms of another. However, Aya's presence lingers in his thoughts, overshadowing any other romantic entanglements he tries to pursue.