Naisho no Kan’in ~Manatsu no Asedaku Koubi~

ナイショの姦淫～真夏の汗だく交尾～
Saddened by the lost of his wife, the protagonist, Ootsuki Kenzou, decided to return to his parents’ home​ in the countryside.

Then about a year later……

Thanks to the wives of his three sons who were sent by them to take care of their father because they didn’t want to see him in such a pitiful state anymore, Kenzou regained his spirit as well as sexual desire. He became aware of his daughters-in-law as women.

He suppressed his lust by masturbating, but then one day, he got caught……

[Translated and edited from Getchu]