It was a very hot summer. Yusuke returned to his parents' house for the first time in a long time. His two older brothers were also there, and his two sisters-in-law were also there. "Both are married." Moreover, they have similar tastes, and both of their wives are "big-breasted." They even have names, Yuri and Yuria. And in front of Yusuke, who is single and without a girlfriend, they are relaxing in a defenseless state, sweating... The stimulation is too strong. Yusuke can no longer bear it and sneaks into Yuria's bedroom, but Yuri notices him...