The brother gets excited when he sees his sister, a high school girl, unprotected in the kotatsu! When she falls asleep, he sneaks into the kotatsu and plays with her, which is hot and steamy! He is so engrossed in it that the sister wakes up, and just when he thinks she will get angry, she touches his dick with her foot and provokes him. The brother gets in the mood and has sex with her! He cums inside his sister, who is trying to suppress her voice so that no one around him will find out!