Kobayashi was Kokoro by the sight at first sight. On the day he came to visit his friend's house, Kobayashi witnessed his friend's mother, Chisato, in her underwear in the bathroom. She was beautiful, but her underwear was unfashionable... Her oversized underwear had nothing to do with fashion, it was only functional. However, for Kobayashi, who was a virgin and had fantasies about women, it was the first time he had ever seen a real woman. Since then, Kobayashi began stealing Chisato's underwear at every opportunity. And before he knew it, he had come to think that there was no one else to give his virginity to other than Chisato.