Oshiri no Oishasan ga, Ore no Ushiro wo Neratteru!?

Dr. Momoki, a renowned colorectal surgeon, has been on a never-ending quest to seek out the perfect ass. When handsome Jin walks into his clinic one day complaining of an itch, alas! In front of him is the most exquisite ass he’s ever laid eyes on...firm and juicy like a succulent apple, with not a hair or peach fuzz in sight. It is an ass sent down by the gods! One examination leads to another...and the two begin exploring the pleasures of each other's bodies.

(Source: Lezhin Comics)