[Mogiki Hayami] Soshite Kazoku ni Naru (COMIC Gucho Vol. 19)

When his feuding parents sign the divorce registration, young Yuuma is handed off to Uncle Minato—the relative the family disowned for finally living as the woman she always felt like inside—and her doting wife Haruko. Between home-cooked dinners, the boy discovers the newlyweds' smoldering bedroom dynamic: busty Haruko savoring Minato's big penis with kisses and prostate-melting handiwork, cooing that her spouse is 'daddy now' while neither can tell who has the dick between them. And with Yuuma peeking through the door at their sweat-soaked finish, this makeshift household is about to become a very different kind of family.