Sayumi is a quiet, obedient, good-natured high school girl who does things at her own pace. She has small breasts and extremely sensitive pink nipples. But because of her obedient personality, she is treated as a sex toy at school. She is toyed with by teachers and seniors, and even her own brother demands her body and she responds. She is forced to perform various sexual acts at school, but the sense of immorality and guilt only makes her more sensitive!