Tsuma ga Ninshinshita Node Dōkyochū No Gimai no Nikutai o Katte ni Tsukatta Hanashi Mo-shon Komikkuban The Motion Anime

The main character's wife is pregnant and temporarily cannot have sex with him. However, he suddenly has a heightened sexual desire that needs to be released somewhere. How fortunate that the hero also lived with his wife's younger sister, Karin-chan. She gladly agreed to sleep with the main character and thereby satisfied all his sexual needs...