Tomohiro, now entering puberty, becomes obsessed with his mother Shiori's breasts. He can't take his eyes off her constantly swaying big tits, fixating on their movement while she cleans or cooks. The soft, large, and erotic shape of her chest deeply excites him. Unable to restrain himself any longer, Tomohiro takes action. Shiori, unaware of his feelings, instead sinks into pleasure, her hips trembling and giving way. Their relationship is now on the verge of a new beginning.