Zettai Ni Itakunai Haisha-san (“Absolutely Painless Dentist”) [English], by Taniguchi-san

Technically, this is a simple gender bender story. Actually, this might be the first time I TOTALLY APPROVE OF GENDER BENDER. Jebus, please have mercy on my soul. The male hero visits a dentist. And, instead of a Gintama-like scenario, he’s offered to swap bodies with a cute female assistant, so that girl will be the one suffering the excruciating pains associated with the ancient art of medieval torture dentistry.

And, while he’s under female form, another cute female assistant jumps on him and proceeds to having sex with her beloved colleague. Watch out, she’s got a penis.
Me : I don’ care, I’d prefer gender bender sex with a futanari rather than dental pain, lol (I also have a useful advice for you about dentist appointments.)
Thanks to Ramza022 for the translation

By the same artist, I also share Mi Kawari Ichinichi Idol, Playtime With A Sexy Doll, and Transform Into Anything, Anywhere 1-2 (also known as Whenever, Whatever, Transform).

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Zip Mirror #1 – or – Zip Mirror #2