Takashi, a working older brother, has a quiet and introverted high school sister named Kotone. One day, he casually uses a "hypnotic ray" he borrowed from a friend on his sister, making her nipples 100 times more sensitive than normal… From then on, Kotone's daily life is completely changed. Unable to stop stimulating her nipples, she incontinently makes grotesque faces while doing so. Takashi, unable to suppress his excitement at his sister's perverted behavior, continuously vents his pent-up sexual frustration on Kotone. Every day, he relentlessly scolds her nipples, causing her to orgasm multiple times, repeating the grotesque faces and incontinence. Afterwards, he uses hypnosis to make her forget everything…