姉ちゃんと家に一緒にいたとき、偶然僕の手がおっぱいの先っぽに当たってしまった。やべ！と思ったのも束の間、ビクンと反応してガクガク震え出して股がびしゃ濡れ失禁してしまった。え！？ちょっと当たっただけなのに、姉ちゃん、乳首が激弱なの？？？乳首がよわよわすぎて反応がおもしろいので、さわさわしたり、つねったり、ひっぱったり…弱点の乳首をねっちょり、執拗に責めまくって、感度をあげちゃったら、ちんこを欲しがってきたので、中出しセックスもさせてもらいました！！

When I was at home with my sister, my hand accidentally brushed against the tip of her nipple. "Oh no!" I thought, but before I could react, she flinched, started shaking uncontrollably, and her crotch became soaked with urine. What?! It was just a slight touch, but my sister's nipples are that sensitive??? Her nipples were so sensitive that her reaction was amusing, so I started stroking, pinching, and pulling them… I relentlessly and persistently teased her sensitive nipples, increasing her sensitivity, and then she started wanting my dick, so I let her have unprotected sex with me!!