The world which was ruled by those called the descendents of god and had unique abilities: Heuk's (Black) clan and Sahwa's clans.

One day, Heuk's clan was destroyed by one of the average human clans, the Parang (Blue) clan. The Sahwa clan sends their heir, Gayeon, as bride to the Parang clan's heir as a sign of obedience.

But the one who's actually sent is the the heir's twin brother, Jayeon. Now, Jayeon lives amongst the Parang clan....

From Easy Going Scans

What happens when you take a good, long look and realize that your boyfriend is prettier that you? And what happens when you go to a high school with so few girls that you're considered a goddess? But then again, your pretty boyfriend is also attending the same school...

The impossible happens in 15th century Korea.

A princess who was disguised as her dead twin brother by her mother became king. Once her true gender is found out, the female king is sentenced to death by drinking a lethal dose of poison.

This story details the events of that forgotten king's life.

From MangaHelpers:
This is a story of a group of college-age people who struggle with gender and sexual identity.
Yuki (nicknamed Yoshiki) is a girl, but she is terrible at 'being feminine.' She mostly dresses like a boy and is often mistaken as one. However, she has to wear a skirt and imagine being dominated by a guy in order to masturbate. Nagao Mikako seems young and innocent, and she uses that apparent innocence to sell her body as a fake 15-year-old. She knows her youthfulness can't last forever, but she enjoys tricking the men. Her friends have no idea of her sexual habits and believe her to be sweet and sheltered. Aiba Kaito is a pretty good-looking guy, but he wants to be Nagao Mikako. He often dresses as a girl, picking out clothes that mimic Mikako's style. Though he's into cross-dressing, he is still attracted to women. Will these young adults and their friends be able to handle their 'guilty secrets' and muddle their way through this confusing period of their lives?

In a country where women rule supreme lives a poor but happy boy named Albert. An excursion to the city turns dangerous when he and his friend are abducted by slave traders, and later purchased by a noblewoman's servant. If this wasn't crazy enough, it turns out Albert looks exactly like the noblewoman who purchased him. But she's no ordinary aristocrat. She's a princess! And he's to act as her double from today on!?

From Go! Comi:

Like most teenagers, Mashiro Ichijo has a secret. But Mashiro's secret is that he’s neither fully male nor female! So far, Mashiro's been able to live his life as a boy, but all this changes when he's informed of a new class he must take in order to graduate from his elite prep school. To pass, he must find the “Key”…and the only way to find it is to enter into a nightmare world where his body and soul are put at the mercy of the worst kind of enemies: his classmates!

A European mystery romance, "Glass Shoes" - the long-awaited conclusion!! The clever Bild, who has figured out that it's Al's spirit currently inside Saylie's body, begins a plot to get rid of Saylie, who will become an obvious obstacle in the future... Meanwhile, Debroyl asks for Saylie's hand in marriage, claiming that he loves her just the way she is, however...?!

Three boys in junior-high who cross-dress because of differing reasons meet each other through a cross-dressing community website, and decide to meet up in real life. "Parou" started cross-dressing because he wanted to attract a heterosexual boy he liked. "Marika" is transgender and identifies as female. Lastly, "Yui" is an antagonistic boy who adopted the persona of his older sister after her death. In contrast to Parou and Marika, Yui is sorely disappointed at the meeting.