ナイショの姦淫～真夏の汗だく交尾～

The protagonist, Ootsuki Kenzou, loses his wife and becomes reclusive in his hometown due to his sense of loss. About a year later, the wives who were sent by his three sons start taking care of him selflessly, and he regains his vitality. However, at the same time, his sexual desire returns, and he becomes conscious of his daughters-in-law as women. He had been suppressing his sexual desire by masturbating, but one day he gets caught.