Koichi, whose mother had huge breasts, has always been interested in women with large breasts, and he was suspicious of his younger brother Yoshiyuki's marriage to the slender Yui. One day, when Yoshiyuki went on a business trip, he accidentally saw Yui No masturbating, who was lonely and had nothing to do with her body. Yui was not surprised by the fact that Yui was masturbating, but by the sensitivity of Yui No beautiful breasts... The next day, when Yoshiyuki returned from his business trip and the couple quickly went to bed, Yui No futon...