Rei, a recluse girl, is constantly subjected to sexual abuse by her stepbrother out of obligation. "Lanchin, since you can't go outside, let me take you shopping instead." He smiles sweetly while asking for something in return. "Since I did you a favor, why don't you make my dick feel good...?" His hardening member grinds against her, arousing him further. He plans on staying in the room until he cums. Everything has become too much trouble, so she reluctantly accepts her brother's demands. However, as his lust escalates, things begin to spiral out of control...

引きこもりの「らん」は義理の兄から日常的に性的虐●を受けている。「らんちゃんは外に出られないから代わりに買い物に行ってあげるよ。」卑屈な笑みを浮かべて優しくしてくる兄はいつも見返りを求めてくる。「お使い行ってあげたんだからおちんちん気持ちよくしてよ…。」硬くなった股間をらんに擦りつけて発情する兄。射精させるまで部屋に居座ってごねるつもりだ。なにもかもが面倒になり、兄の要望を受け入れるらん。しかし、義兄の性欲が次第に暴走していって…。