Attracted by her boyfriend's sister's unguarded, exposed breasts and lack of a bra, she couldn't help but stare! Taking advantage of their time alone, she pointed out that she wasn't wearing a bra. Shy and unable to refuse, she just went ahead and had sex with Ogasawara Nana. (START-567)

Shiro, staying at his friend's house, is unaware that his friend's younger sister, Nana, has a crush on him. He can't help but stare at her defenseless, braless state. The bra he accidentally finds in the dressing room is shockingly large—an I-cup. Overwhelmed by the shame of sleeping next door to his brother, Shiro forcibly hugs Nana, who trembles with shame after being pointed out for not wearing a bra. A passionate first love unfolds, a story of pure, intense love with a busty beauty.