From Operation Boredom:
Yamato Onidzuka. Childhood bully, punk, and sports prodigy. His old childhood friends are terrified of him, as he used to bully and harass them on a daily basis. When he transferred to a special sport's school, it seemed like his friends' worst nightmare had finally come to an end. But now that he's back, it seems like the nightmare has returned.

Taiga Shishio, the Student Council President, is a notorious tyrant. And yet, the only person that can stop him is his faithful Vice President Momoko. School, love, and trouble collide in this amazing story of student leadership!

Oneshot: Bitter Trap
Nanao came from a rich family before their business failed. Now the only hope for her family to pay off their debts is if she can cement a marriage with the prestigious Takatsuki family within a week. How will Nanao overcome this problem when one of the three eligible Takatsuki men is her former arrogant schoolmate, Yoshito, who completely distrusts people? And did we forget to mention that Nanao is already the ninety-ninth candidate for the position of future wife?!But is she really there to pay her family's debts or is it for....
- Aerandria Scans

From Aerandria Scans:

Kei is a girl who's only interested in other girls! However, tricked by her mother, she enrolled in an all boys school, thinking that she'd be able to make her high school debut at a co-ed school. To normal girls, being surrounded with hot guys at an all boys school might be heaven, but to Kei, this is hell! What is Kei to do at this place without any other girls, where she has to try her best to keep her real identity a secret?!

What is a sweet, soft-spoken girl (Ha Li Kang) to do when her brothers, having just learned fencing and martial arts, decide to test some moves out on her in order to "tame her" and make her into their "little slave?" She runs to her knightly friend (Te Hu Kang, not related to Ha Li) for protection, of course. However, what happens when, instead of comforting her, he tells her that she is a coward for running away like a puppy who needs constant protection? No, she does not break down and cry like a weak girl. Instead, she resolves to grow stronger. With rigorous training everyday, Ha Li goes from being a scared girl who cries for help to becoming the Jjang (boss of a gang) of the Doberman gang. However, events lead to Ha Li getting in an accident with a truck. Afterwards, she is reborn into the body of a beautiful, but weak, rich girl Aram Han.

At her new school, everyone is surprised at the sudden change they see in Aram, who has gone from a gloomy, good student to a rude, carefree troublemaker. Many people bully her. When Ha Li finds out that it is all due to Sin Uoo Park, the handsome prince and Jjang of the school who detests Aram, she decides to have a duel with him for the position of Jjang. What will happen next is for you to find out in this romantic comedy Korean manhwa.

1) Zenbu Shiritai
(I Want to Know Everything)
I won’t act spoiled in front of my boyfriend, and I definitely won’t trouble him, either. I’m trying to act like a cool and mature ideal girlfriend, but the truth is, I’m a persistent and annoying girl who wants to be pampered by her boyfriend! Even though I'm hiding my true self from him, to satisfy my evil desires, I’m stalking my beloved boyfriend!!

2) Sakasama Honey
(Upside Down Honey)
Kameyama Chisato is a girl without boyfriend, because of her sadistic personality. While trying to fix it by secretly practicing with a skeleton in the Biology lab, a classmate named Kurosawa Akihiro sees her. What will happen to her secret?! Will Chisato ever find love??

3) Chiru Chiru Michiru
(Fall, Fall, Rise/ Broken-hearted Michiru)
Michiru is a girl with poor luck when it comes to love. She’s been dumped several times by her boyfriends for other girls. After her latest breakup, she feels really dejected. In her attempt to get over her love, she pretends as if she's about to commit suicide. However, a boy from her school, who is rumoured to be a delinquent, stops her, and promises her that he’ll introduce her to the best guy on earth. Just who is this 'best guy on earth' and where can he be found? Or is he right in front of Michiru’s eyes?

4) Ashita Hanabi ga Agattara
(When There's Fireworks Tomorrow)
Tomoe has a dreamー to go to the fireworks display during the summer together with the guy she likes. However, she hasn’t found that spark of love at all, at least, not until her childhood friend, Miki, moves back to her school and she meets Kagami through him! She makes the perfect plan to confess to him, but that doesn’t go as well as she had hoped, when Kagami confesses to her that he really likes Tomoe’s best friend, Rikka! Is the friendship ruined between these best friends now? And will Tomoe be able to fulfill her dream of watching the fireworks with someone she loves?

5) Super✰Star
There’s a certain group of guys in Kiyoko’s class that stands out, and to Kiyoko, Hoshino stands out the most! In fact, whenever she sees him, he looks like he’s sparkling. However, Kiyoko realises that Hoshino isn’t exactly what he seems to be, when she discovers him working at his family’s run-down convenience store! But even in his dull work clothes, Hoshino is still sparkling to her. But it’s not until Hoshino is confessed to by another girl that Kiyoko truly realizes that even if she’s different from Hoshino’s ideal girl, she still has a chance… but is it too late now for her?

From Tenshi-Tachi:

Yanagisawa Aiku is the president of the flower-arranging club. In order to save her club from being closed down, she agrees to go out with Hosaka Ryousei, the extremely handsome president of the student council. However, the only problem is that Ryousei is always in love with one girl after another. Aiku is just another girl to him... or is she?

Mingyum wants to become East Asia Strongest martial artist, however, he has no Zen, which makes it impossible for him to reach that goal.

One day, he gets lost and finds a group of thugs, in an attempt to save a girl, he gets beat up. But in the heat of the fight, a blond foreign girl saves his life while claiming to be his fiancée. Almost at the same time, an accident occurs and Mingyum discovers he can use a huge amount of Zen, if only for a limited amount of time.

What will happen next?

A regular school boy, Hikaru Shindo stumbles upon an old GO board while looking through his grandpa's old storage room for something worth money. From inside the board came an old spirit named Sai who once dedicated his life to GO. Together, Sai continues to search for the move people call "The god's hand" while Hikaru slowly began interest in this ancient game and walks down the road of GO.

Won the Shogakukan Manga Award in 2000.

Hardworking level one magician Konoha is apprenticed to lazy Knight Protector Saionji Ikumaru. They both work to keep the ether world sealed away from their own but sometimes the seal doesn't work. Dragons, demons, and now Ishtar, the goddess of Venus. Will Ishtar help Konoha win her master's affections? Or will she take him for herself?

From Wild*Hope:

Miyako, who has undergone strict training, is the heiress of a rich family. However, the person she loves is her distant cousin Chiaki, who is her complete opposite. Miyako's mother has always been opposed to their relationship and arranges an omiai for her. Just when Miyako prepares to elope with Chiaki, she finds out that he has already left...?

In a small village, there is a legend about a person born from a sakura tree one thousand years ago. Though she appeared human in form, she could not understand love, and was therefore cruel. She was eventually destroyed. Now, the mythical Sakura tree is going to attempt to create human life once again. This time it is up to two high school students, the incredibly beautiful Tasuku and the love-allergic girl Honomi, to teach the Sakura Child about love.

Utsuru Sanada is a professional photographer at the age of 17, he can guess the exact 3 sizes of any girl, he can memorize anything he sees, and he can counterattack karate moves (most guys would want these abilities). Why? Because he has superb photographic memory called “Shutter Eye”. He meets Niko Kurihara, the female protagonist, who dislikes men, is a master of martial arts, and is of course beautiful. Utsuru attempts to prove to Niko that he is not the guy she thinks he is so that he can take a picture of her. He starts by investigating Niko’s friend’s date, who appears to be a deceptive guy according to rumors…

Ran as a one-shot in 2009; started serialization in 2010.

Saiki Takaya, a guy who is easily misunderstood, one day finds a flask containing the succubus Lilim. She is very attractive but, she also has the tendency to drain the life force out of people. She surprises the life out of him (literally) when she kisses him unconscious. Lilim then flies off for more "food," but returns later, saying that Takaya's life-energy was the "tastiest." From then, Lilim is accepted by Takaya's parents as a live-in girlfriend of sorts, and Takaya's heart seems to start wavering towards this voluptuous devil.

From RebelliousArt:
Asahi, desperate after the loss of her best friend and boyfriend, came to the abandoned elementary school above the hill. It has been said that it's a cursed place that it will be the last place you will tread in. Those who live will not be able to return. And there, Asahi meets...!?

A series of oneshots.

Sana Kurata, a child actress, faces many problems in her classroom, including a major one - her bullying classmate, Akito Hayama. Sana's outgoing and friendly nature leads her to work towards correcting all of the problems around her. Her 'meddling' irritates Hayama but at the same time captivates him, just as Hayama's gloomy nature irritates Sana and compels her to change him. As these two opposites attract each other, they face many hardships which bring them closer to a mutual understanding.

This manga won the 1998 Kodansha Manga Award for shōjo.

Daisuke is a 23 year-old new schoolteacher. He ends up being put in charge of a 3rd grade elementary school class since the previous teacher quit, and in that class there's a girl who's quite a troublemaker--Rin Kokonoe. You could call her a masegaki (used to describe a kid that acts more like an adult in some ways), and she's also part tsundere (though more dere than tsun).

From Del Rey:

Najika is a great cook and likes to make meals for the people she loves. But something is missing from her life. When she was a child, she met a boy who touched her heart–and now Najika is determined to find him. The only clue she has is a silver spoon that leads her to the prestigious Seika Academy. At Seika she meets two brothers Daichi and Sora, could one of them be the boy from her childhood?

Won the Kodansha Manga Award for Children's Manga in 2006.

Fujita is a second year middle school student with a face as pretty as a girl's. On top of that he's whimpy and a bit of a crybaby so he's often confused for a girl. Echo-chan is a fairy who promises to grant his wish and turn him into a strong and attractive man capable of sweeping Onigasaki, his unrequited love, off her feet if he agrees to help her.

From Karma Falls Scanslations:

Because of a frightening experience three years ago, the boy Sata Senda became a compulsive cleanliness freak. As he has anti-bacterial spray and mask as standard equipment and doesn’t allow any form of close contact, he has no friends… Thus came the summer of sixth grade. Sata, who has been half forced to participate in the school trip, arrives to the meeting place completely wrapped in a protective suit?!

From Taruby:

Our protagonist, Moji Shimeta, just so happens to fulfill the stereotype for being a worthless human. His inability to carry out a conversation has left him at the bottom of the barrel as far as friends are concerned.
That Shimeta fell in love with the school idol Ishikawa Yuuko, however that kind of love is absolutely, perfectly, and completely impossible. During this time, the messenger of the gods, Osaki, appeared to grant Moji's request with a price attached concerning Moji's cooperation in catching some runaway evil spirits. However to catch them all, Osaki uses Moji as a vessel to become a servent of Uganomitamanokami (aka Inari) called Youko. Lots of Ecchi situations and humiliation abound at Moji's expense.