Minami lives with her boyfriend and his younger brother. One day, while her boyfriend was away, she received a consultation from her boyfriend's younger brother that he had gotten a girlfriend for the first time but wasn't doing well because of premature ejaculation. Since her boyfriend wasn't there anyway, she thought 'whatever' and started training him to fix his premature ejaculation problem using various methods. Seeing her younger brother-in-law trying so hard made her feel fond of him, so during the times when her boyfriend was away, she began a slow and thorough training session to improve his premature ejaculation, even using her own vagina…
