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.

This is a story about 2 childhood friends, Masato and Yuki, that reunite as teenagers. Masato is surprised to find that Yuki has become so cute, but even more surprised to realize that Yuki was, and still is, a guy. Yuki's affection for cross-dressing leaves Masato with feelings of discomfort and fright.

On the last day of school, Mihane confesses to her senpai the long-term admiration she's had for her ever since they met, as well as tells her that she will try her best to enter Niji no Oka Girls' Academy next year, the school to which her Senpai is going to attend. Now, one year later, she's managed to pass the entrance exam to the prestigious school and is taking the bus to the school. Unfortunately, she takes the wrong bus, but encounters an interesting first-year girl, like her, that is also set to attend Niji no Oka Academy.

Yoshino Nako has a saying. "If I'm happy, I can do anything!"

In her sister's place, Nako-chan steals the groom of an arranged (political) marriage and helps them elope. But when the Hayami group starts failing, she must pay the consequence by housing the delinquent brother...

From Perfect Illusions:

Reo-chan, a first-year girl, gets dumped by her boyfriend because she's not skilled in the home economic traits he believes women should have. Her ex tells her that she must apply to a "housework" club before he will reconsider going out with her. Therefore Reo-chan has little choice but to join.

Here's the catch: the only members are four gorgeous bishies. The other first year in the club, Irinaka, competes with her a lot. As the story progresses Reo and Irinaka get forced into a lot of interesting situations together and in the meantime become closer and closer.

Being beautiful is never easy, especially if you're an eighteen year old boy like Yoon Da In who is constantly mistaken for a girl because of his delicate good looks. Da In is, in fact, anything but delicate. He is the ringleader of a group of tough kids in an all boy's school, and he's quick to beat the living daylights out of anyone who even hints that he resembles a girl. If that wasn't hard enough for a regular teenage guy to cope with, his life is about to take a shocking turn for the worse. When Da In stumbles upon strange happenings in the forest, he gets sucked into a world of vampire intrigue and sinister romance that he never knew existed. And he learns that there are worse things than being turned into a vampire: being turned into a girl?!