From RC-SCANS:

Gook Eun-Song is your average high school girl... that is until her attractive younger sister stole the man she had a crush on. Depressed, Eun-Song purchased a bottle of alcohol and crawled into a supposedly cursed closet in her father's furniture store.
Yu Ha is your average typical bad boy. Going insane over one article in magazine, he even broke traffic regulations while drunk just to end up being chased by a couple of police officers.

Oddly enough, he also ended up in the same closet where Eun-Song is asleep from drinking too much. Yu Ha ends up sleeping in the cursed closet with Eun-Song by his side... just to find out the next day, their bodies have been switched!

Can anything else possibly go wrong for our poor heroine?

STYLISH ACTION FROM THE AUTHOR OF ARCHLORD! The new English teacher, Chun-Woo, is not your ordinary teacher. Shioon, a victim of constant bullying, unexpectedly witnesses Chun-Woo's fighting power, and begs him to make him his disciple. Chun-Woo claims he can teach Shioon only if he is truly determined, and Shioon must jump off a bridge into a deep river in order to prove it! It turns out, however, that Chun-Woo and his powers are more than meets the eye. Shioon makes a grand entrance into the hidden world of martial arts, and he is about to be taught by the best there is! You can read part 2: The Breaker - New Waves here.

Manhwa you may like:
+ The Gamer - ​THE 게이머
+ Gosu 고수
+ Yongbi The Invincible 용비불패

The demon queen subdued enormous and powerful monsters and slaughtered over half of the world's population. Surviving members of the human race elected a hero to slay the demon queen, beseeching release from her oppressive rule. However, he questions his mission to eradicate the monsters: in his opinion, they too are conscious and alive, and so he anguishes over that fact. Sheila the Demon Queen became interested in him and decides to join his journey, hiding her identity and planning to kill him after she has gained his trust. Immediately, however, she realizes that she's fallen in love with the hero, and hence their journey begins...

With his phrase "don't you dare make girls cry," Makoto Tobita has failed his 30th confession, but that won't stop him. Promising to do anything for the girl who smiles at him, no matter what it is, what will happen now when the alien fighting - giant girl, Mana Eimiya, is in love with him?

A spin-off story focuses Kazuma Ikezawa (King Kazuma), Natsuki Shinohara's cousin, as he battles his way in the Oz Martial Art Competition.

He is Europe's most sought after bachelor, worth over 10 billion in assets and the most handsome young master: Louis. Yet he fell in love with the Olympics Taekwondo Champion Lee Le Ting. So Louis tries all he can to get closer to her...

The heroine of the story, Amu Hinamori, is a student at Seiyo Elementary. At first glance, her classmates refer to her as "cool and spicy" and rumors speculate about her personal life. However, her real personality is that of a very shy girl who has trouble showing her true personality. One night, Amu wishes for the courage to show her "would-be" self, and the next morning finds three brightly colored eggs—red, blue, and green—in her bed. At first, she is alarmed, but realizes she must have really wished to change. These eggs hatch into three Guardian Characters: Ran, Miki, and Su. The Guardian Characters aid Amu in discovering who she truly is and help fulfill Amu's dreams. Amu's life becomes much more complex as she struggles to deal with her "would-be" selves and the Seiyo Elementary's Guardians, who recruit Amu as the Joker to search for X Eggs and X Characters, the corrupted forms of peoples' dreams. Meanwhile, the Easter Company is extracting people's eggs in search of a special egg called the Embryo. The Embryo is believed to grant any wish to the one who possesses it. However, the process creates X Eggs and X Characters. Continues on "Shugo Chara! Encore!"

Mashiro was always alone, whether at high school, cram school, and home. Until one day, Mashiro met a youngster with a strange atmosphere. Holding the thought of “I want to change”, she took a big first step forward--even though her legs are small--seeking the path of Eden.

Energetic and strong-willed, Beni doesn't care if she lives or dies as long as her death will result in embarassing her arrogant father! But one day, she suddenly encounters Kagetora, a ninja who's fallen from the sky and swears complete loyalty to her -- as her bodyguard. Kagetora has time traveled from a long, long time ago, and has devoted his life to protecting Princess Beni. Little does Kagetora know that this Beni is not the real princess... Can true love and honor survive after a centuries-long time warp -- in a crazy modern world?

Furoku is a Shinigami who fell in love with a girl, Himeka, while waiting 6 months for an old man to die in the hospital. The problem is, she is supposed to die in heart surgery, and not only that, she's meant to go to hell. The reason being, she was born with a weak body, but dreams of taking over the world if she had a stronger body. So, Furoku offers some of his life up to save this "girl who hasn't done anything wrong". What future lies ahead of Fukuro and this "Bloody Queen"?

From: Easy Going Scans

Deadly chemicals, lab rats, mutations to the genes and a mysterious case of death. Shamans--the people who can see and treat the dead. One of them often spies a girl--the girl his step-brother choked to death.

From FairGame:

"Live with Sincerity" is Natsuki Taiyou's motto. It's the first day of high school, Taiyou was heading to school and then he meets Hinata during the way there. He fell in love at first sight and suddenly confessed to her. Her answer was yes but then she ran away without saying who she was, but it turns out that she was his classmate. Taiyou felt a destiny between them. However, on the next day, she doesn't remember who he is. Why could that be...?

Contains 4 fantasy stories (2 plausibly tying into the main story), 1 story taking place after Harima announces he's a mangaka, and 5 stories occurring after the final chapter (with 2 being a part of the possible future)

In a modern country where the government is controlled by a Martial Shogun and samurai receive much respect, there lives fraternal twins of the Sakakido family. Kou, the brother, is very feminine, excels at cooking, cleaning, arts and crafts. Tsukiko, the sister, is masculine, loves fighting and is a combat genius. The twins learn about the Samurai High School, where men test their strength and women test their femininity, but the only way they can attend is by swapping places. If they are to be found cheating, they will be exiled so they have to overcome their gender differences and maintain their secret.

From Shoujomagic: Haruka is a sweet, innocent high school girl who is very excited to meet her new step-brother, Tsukasa. Since her father works overseas, Haruka has been living alone, but now that her father has remarried, she'll have little grade schooler Tsukasa with her while both their parents are out of the country. When they finally meet, Tsukasa is even cuter than Haruka had hoped! He wants to get her help with his homework and sleep in her bed...and undress her and make love to her!?

「 Don't Interfere with My Life!! 」

Handsome face and all around sportsman, also the young master of an enormous rich family...Chung-sol High school's No. 1 Han Sang-Ah!! This young master who doesn't lack anything ventures running away from home?! Officially permitted runaway time is 3 years! During this time there is something he says he must get in his hands...!! From then on starting to confront him are woman!! woman!! women!!!

Harem Flood Mixed with Comedy and Action! Explosion of Heart Fluttering Pink that would tail all Korea's Bookstores!!

(Source: volume one's backcover)

A talented young man who doesn't want to be an official. A beautiful, intelligent young lady who hates to be looked down on by men. When these two meet in a very uncomfortable situation, a big argument arises. Will everything settle down, and can these two talented people find true love when there are so many obstacles ahead?

Senguu Fumihiro is a young boy that made a promise to his dying grandmother to find a good wife for himself. With this intention he enrolls in a prestigious school but on the first day his world turns upside down when all the students begin to kill each other and one of them even turns into a monster. He is saved by a girl named "Akari" sent by one of the factions that rule the school to protect him. From Baka Updates

Watanuki Kimihiro is a high school student plagued by yokai and ayakashi – spirits with a strong attraction to him. The spirits are invisible to others and encounters with them are extremely troublesome. When he stumbles into a shop that grants wishes, however, events in his life promise to become more unusual. The shop is owned by Yuuko Ichihara – a mysterious and beautiful (sometimes playful) witch of many names and esoteric renown. For a price, she offers to grant Watanuki's wish to be rid of the spirits. The price, according to Yuuko, must be of equal value and so, as payment, he temporarily becomes Yuuko's part-time employee – a maid to be precise! Watanuki's job also seems to consist of small errands dealing with the supernatural including the household chores. His love interest Himawari Kunogi, and "rival" Doumeki Shizuka, occasionally join him in his work as per Yuuko's request. The three become increasingly close despite Watanuki's annoyance with Doumeki. Yuuko constantly refers to "hitsuzen", meaning inevitability, destiny, or fate, as being the driving force in the world. She states that there is no such thing as coincidence, and that every single action and decision is inevitable, because without them, other related events in the future could not happen.

From JShoujo Scans:

Although she doesn't get along with people very well, Kanoko considers herself a perfect "observer". Her hobby is observing the students in her third year junior high class and keeping a journal of the classroom drama. But what will happen when Kanoko becomes involved with some of her classmates?