Rin Aoki (25 years old), married to an older husband, is living a happy life. However, for my son-in-law who lives with me, Rin's mother-in-law's big butt is too obscene, and he repeats delusions while looking at his mother's butt every day. One day, my son-in-law saw Rin wearing sportswear for a diet and exercising while shaking her buttocks...