Meat has been the trainer of the great Choujin superhero Kinnikuman for long. He thought his job was done helping his greatest subject become a master Choujin and king of his homeworld. But what if upon waiting for his next subject, the little trainer was sent to another world? A world where Kinnikuman has yet to become a great hero and a world where he is... female?

From Tokyopop:

A dad that's a professional model passed on his stunning male looks to his only child, Kiri...but unfortunately, that Kiri is a girl! Tohya Enishi, the love of her life, decides to be a male model, so Kiri fakes her gender and becomes a male model alongside him. But things get really complicated when others start to fall for Kiri and her male alter ego!

Let's just say my best friend's... a magical girl.
The Cocktail Nights are popular, secretive battle maidens who cleanse the people of their stress. No one knows of these girl's true identity... well they shouldn't! Only I, Riku Daichi (long time unrequited), knows of one of their secret identities. But we have to keep it under wraps. Presenting a love-comedy with confidential-levels of mistakes!

Minami-kun spots a poster recruiting new members for the Magical Girl Club. Thinking "Cosplay cuties woohoo!" he decides to join... What the hell!? It's not cosplay—we actually become magical girls??

A slice of life love-comedy revolving around magical girls and slippery slopes.

From MangaHelpers:
Nogawa Izumi is a good student, and a class representative, but she has an increasingly high libido. It's gotten to the point that she'll claim to feel bad during class, so she can run to the nurse's office and masturbate. When she learns that the Earth is being invaded by aliens that look like people dressed up as animals, it turns out her high sex drive may be able to help protect the Earth. The first time Izumi is attacked by the aliens, she is rescued by Usayama, a bunny alien whose race was their previous victim. Usayama gives her a swimsuit that will allow her to fight the aliens, but which also sends her constant arousal through the roof. The scientific organization that Usayama is affiliated with think that Izumi, with her high erotic level, may be the person they've been looking for to fight the aliens. Will Izumi be able to save the Earth?

Naruse Soushi is a 38-year-old political secretary. One day, he is caught in a car accident, and his vehicle is swept to the bottom of the sea - with himself in it.

At the same time, in a completely different world, a princess named Reina is caught after her kingdom is taken over by another country. Her retainer, with no other options left, decides to save her soul by taking it out of her body. Searching for another soul to replace it, she chooses Naruse’s.

And so Naruse - now in princess Reina’s body - is taken prisoner and sold to a lesbian brothel. Taking up the name Lillion, our protagonist decides to embrace being a prostitute and rise through the ranks, to both attain a more comfortable experience as well as figure out the mystery behind Reina’s past.

Both of them are straightforward people. Once they meet, they quickly get to know each other better. A heartwarming romantic comedy that begins with a certain incident. Shibata Kasane, a graphics designer at a toy design and development company, is troubled. Her troubles started when she grabbed her colleague Enokida Subaru's ass by accident! Kasane was intrigued by how similar Enokida's ass and her favourite childhood character felt. At the same time, Kasane felt guilty because Enokida might have been uncomfortable. Enokida said "I don't mind" but had a pained and frightened expression. Kasane was overcome by the urge to apologise profusely! On the other hand, it looks like Enokida is hiding something.

I found myself possessed in a game I used to play occasionally.
And to top it off, I'm the female warrior of a barbarian tribe that only has bad endings.

...Alright, let's escape.

From Intercross:

Kurosaki Mafuyu was a juvenile delinquent and head of her gang before her subsequent arrest got her expelled from high school. Now that she’s transferred to a new high school, she’s determined to become an “ultra-shiny, super feminine high-school student.” But with a new friend like Hayasaka-kun and a homeroom teacher like Saeki Takaomi (who may be more than he seems), will Mafuyu really be able to live a girly-girl high-school life!?

From Aerandria Scans:

It's the 16th century and the knights of the Mediterranean country Malta take pride in being the strongest in the world. Aciel is a beautiful lady-knight who gradually makes her way into the group of the knights, despite the fact it's forbidden for women to be knights. Learn the tale of the magnificent knights whose charms neither friends nor foes can resist!

From Condensation: Although Gyu Hwa Lee might look like a guy, she has feelings like any other girl. In fact, she's currently in love with Korean pop idol Kang Un Ryu. As luck would have it, Kang Un ends up transferring to Gyu Hwa's high school. The only problem is he has to keep his identity a secret so he's cross-dressing as a girl! What happens when Gyu Hwa discovers Kang Un's secret? Will she ever be able to win over his heart? Or will she always be nothing more than just a friend? A Korean manhwa with surprising poignance and refreshing humor by the author of Cynical Orange.

A boy's older brother gives him a potion that turns him into a flat-chested school girl.

What if the person you liked was the same gender? A beautiful girl suddenly appeared in front of the main character, Yuji! But what's her real identity...!? A new generation love comedy that questions “true love” in between tales of laughter and sadness.

Keito Azumi, an ordinary high school boy, was reincarnated as the heroine in a different world when he woke up in an accident! The worst thing about this is that his best friend became the hero!

Stories following various adolescent girls and their encounters with puberty and other worlds.

Marimo Himenogi desperately wants to become an idol singer. When a local contest is announced, she begs her boyfriend, Ayumi to sing as her partner. Ayumi relents, and disguises himself as a girl so that he and Marimo can enter the singing competition. Surprisingly, they win and are signed to a recording contract as a new group called "Twinkle". Now they must keep their newfound fans from finding out that Ayumi is actually a boy.

Shirokawa Sasane (30) is a former trading company employee and a huge fan of Romance of the Three Kingdoms. One day, after losing consciousness in Chinatown, he wakes up to find himself in the form of a little girl. However, the new body he finds himself in isn't just any little girl, but the granddaughter of the infamous tyrannical Dong Zhuo, Dong Bai. In order to avoid the fate of being executed alongside Dong Zhuo, Dong Bai will have to use both experience as a Japanese businessman as well as knowledge of the era!

Born as the illegitimate second son of Loxollum’s king, Iblonde is sacrificed by his pagan mother to ensure that one day, he sits on the noblest seat in the kingdom. A few years later, Iblonde has started a new life as Abel, a serf of a baron’s domain. Aside from his tragic past, Abel harbors many secrets, including the fact that he is actually a girl. But the greatest secret of all is that Abel’s resurrected body is now occupied by Belial, the seventh king of hell, who has come to slowly plague the land...

At first glance, the Fukuoka city seems like a peaceful one, but under the surface, crime is running rampant. The city's Hakata ward is home to the professionals of the underworld: professional killers, detectives, informants, professional revenge seekers, those skilled in torture, and more. And according to urban legend, even a “killer of professional killers” exists in the city. When stories of the men in the underworld are told, a “professional killer murder” appears.

At Fumidzuki Academy, classes are separated by academic achievement. The smartest kids are in A Class, while the dumbest are in F Class. This chronicles the daily life of the students in F Class. Instead of grades, they have to worry about homosexual stalkers, crushes, ambiguous genders, and waging academic war on the upper classes!