Onna Ni Sareta Maou-sama (“The Demon King Who Was Turned Into A Woman”) [English], by Demio
Rather than slay the demon king, why not lay him, right? All it takes is a little gender bender magic, and there you go, you’ve saved mankind AND you’ve found the perfect babe, with huge breasts, an hourglass figure, and delicious-looking dark skin ┐( ̄ヮ ̄)┌
Gender bender logic evades common sense, as always, but hey, it’s kinda funny and there’s plenty of eye-satisfying material, usually not too censored, so I’ll roll with it lol.
Release credits are for Espeon and Hennojin’s NekoHime, Baran and Phalodite, thank you!
And now, the download & gallery links 
Open the Complete Pictures Gallery
Download the Free Hentai Manga in a Zip file
(52 MB, 19 pictures, English)
Or you can also use the Alternative:
Zip Mirror #1 – or – Zip Mirror #2 – or – Zip Mirror #3
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Smaller version incoming!
As of usual when ☑ the images are in high enough resolution and ☑ the archive is quite big for its number of pictures, and ☑ it offers a significant gain, and ☑ I have enough time to do it, if it may help, I’m offering you a smaller version, in which I resized the images, here from 3000 px to lower-standard 1600 px resolution.
The zip shrank from 52 MB to 13 MB.
Personally, I prefer it for reading, and it takes less disk space.
Download links, Zip: Mirror #1 – or – Mirror #2 – or – Mirror #3 – or – Mirror #4
Hero draw sword in front of demon lord and nothing happen to him?
potion over powered?
welcome to hentai my friend.
There is too many things that do not make much sense, even for a genderbender doujin.
Personally, I take comfort that this sort of thing will never happen to THIS Demon King, except in the twisted mind of some manga or douuin artist:

And if one day an artist should try to do so, I’ll sic the “orbiting death cannon” on ’em … figuratively speaking of course.
If you can’t beat them, fuck them.
For me it has too many vibes of ye olde “If I just treat a girl like shit and fuck her into oblivion, she’ll surely fall in love with my cock and call me darling”-hentai trope.
Gender-bendering a “Demon Lord” into a girl is a very sorry excuse and the “hero” isn’t really better than the despicable guys Oliver detests so much.
Well, just my 5 cent.
My take on this is the hero declaring “Be mine, demon lord!!” and the demon lord going “I refu–wait, shouldn’t this be the other way around!??”