親友の家に泊まったシロは、妹・菜乃が自分に寄せる密かな恋心を知らぬまま、彼女の無防備なノーブラ姿をガン見してしまう 。脱衣所で偶然手にしたブラは衝撃のIカップ 。兄の隣で眠る背徳感の中、ノーブラを指摘され羞恥に震える菜乃を強引に抱きしめる 。初恋の熱情が溢れ出す、巨乳美少女との純愛ハメまくり物語 。
Staying at his best friend's house, Shiro is unaware of the secret feelings his best friend's younger sister, Nano, harbors for him, and finds himself staring intently at her defenseless, braless figure. In the changing room, he accidentally picks up a bra and is shocked to discover it's an I-cup. Sleeping next to her brother, Nano trembles with shame when he points out she's braless, and Shiro forcefully embraces her. A story of pure love and passionate encounters with a busty beauty, overflowing with the passion of first love.

– JavGG.net