Mizuki Sakamoto runs a classroom teaching kimono dressing, but she charges no tuition or enrollment fees. After losing her husband three years ago, conversing with people became her only joy. Today, Principal Nagatsuki arrived for a private lesson with Mizuki. He advised her to wear a fundoshi instead of panties when putting on a kimono. Once tied, the fundoshi presses tightly against her crotch, creating a strangely pleasurable sensation that inevitably leads her to masturbate.