Shiro stays over at his best mate's place with no idea that Nano, the mate's adult sister, has been quietly in love with him — and ends up staring at her braless. The bra he happens to find in the changing room turns out to be a shocking I-cup. With the guilt of doing this while her brother sleeps next door, he pulls a trembling, humiliated Nano into his arms after calling out that she isn't wearing one. A pure-love story of fucking a busty beauty, with the heat of a first love spilling over.