Yumi, a wife who is troubled by a sexless marriage with her husband. One day, when she finds out that her husband is cheating on her, she decides to start "improving her physical condition through yoga = mankatsu" on the advice of a friend who has the same problem. As she continues, her body begins to change, and her husband also becomes more proactive in their nighttime activities... Just when she thought she had finally resolved her long-awaited sexless marriage, her nephew becomes aroused by the effects of mankatsu! Yumi's body has become so sensitive that she can't resist her nephew, and he even teaches her how to squirt for the first time...