Title: "A drug that turns you into an adult 1."

Plot: guy tries to get his sister to take a drug saying "it will make you super smart." Instead she makes him take it and he turns into a busty woman in part 1.

There are 3 expensive sequels where he probably has sex with his Imouto, and is ravaged by a man with age regression elements.
http://www.dlsite.com/books/work/=/product_id/BJ068501.html

It was also serialized in マガジンサイベリア Vol.079 onward, which we don't have.
Parts 2-4 here:
https://e-hentai.org/g/939102/7bace15f97/
https://e-hentai.org/g/939105/9ee6b878e0/
https://e-hentai.org/g/939106/648b895068/

If you like my work, I've started more gender bender bounties for unshared manga so remember to support them:

https://e-hentai.org/bounty.php?u=413256

in term of gender bender story , I always like okawari work , great overall from drawing and storyline ^_^

like in that great onnanoko manga ^_^

Base +23, Epion +20, sentrin +8, Whabash +7, エロ魔人 +9, jarry334 +5

So it takes something weird like gender bender for us to get a hentai that's focused on female masturbation. We'll never get one about a normal chick who's just a closet freak, will we?

Base +17, Ooe Kintarou +5, エロ魔人 +9, jkezer -10, Refyrsen +6

Okawari is a totally underappreciated artist, thanks. Age regression is a bit of a let down, mostly cause I really did Okawari's short haired girls.

Base +7, Lance_mc +15, エロ魔人 +9, hondawhr +24, ZHKC21 +6, rjimenez666 +5

Doesn't the 18th image come from an other manga?

Base +6

http://book.dmm.co.jp/detail/b171bkocb00257/ I thought it was odd that the girl with black hair later on 'looked' different. My First thought without knowing the plot and following just the pictures I thought it was the 'sister' like character in the first 2 chapters. It seems like their's a page missing with the guy who gave him the pill. If you click on the button under the picture of the cover and look at previews, we see the 'friend' giving him the pill. Small detail, but definitely changes a lot of perspective there knowing there's another character in it.

My big problem with this series is that the cover and first chapter tease us with an appearance for the main character that is pretty much non-existant. After the first chapter, that wonderful 'short haired' beauty is turned into a loli. Nothing against loli's, but I really like short haired TGs like that and it was a shame to see it pretty much be pointless to have 'her' on the cover.

Base +6, Pikachus73 +6

I'm surprised no one has translated it since it'd be easy to do, and it's a fairly enjoyable series. I feel sorry for everyone who is missing out. Learn from this - learn Japanese because of how unreliable we are when it comes to translating better material. (Btw she's not a loli, she is just petitie.)

Base +16