Naisho no Kan'in ~Manatsu no Asedaku Koubi~

After losing his wife, protagonist Ootsuki Kenzou retreats to his hometown, consumed by grief. A year later, the wives sent by his three sons begin caring for him selflessly, restoring his vitality. But as his strength returns, so does his sexual desire, and he starts seeing his daughters-in-law as women. He'd been suppressing his urges through masturbation—until one day, he's caught.