A shounen story where 2 teenagers went back in time to the "Three Kingdoms" period of China. An entertaining action series with some light moment & a bit of romance. You also get to learn a bit about that era.

From JanKenPon:
Middle schoolers, Shiro and Masumi, encountered a mysterious dragon that brought them back to the time of the Three Kingdoms; situated in ancient China. As soon as they arrived, they were rescued by the Han Kingdom. Not long after these events, Masumi was kidnapped and Shiro barely escaped death... Soon the story gets more complicated as they are stuck in the past.

In 1997, Ryuurouden won the Kodansha Manga Award for shōnen manga.

Aka Abarenbou Kareshi

1) Rough ♥ Boyfriend (first part)
2) How? ♥ Boyfriend (second part)
2.5) It Is Difficult to Understand! ♥ Boyfriend (extra)

Naoto is Hajime's childhood friend. Naoto may look cute but then again, his attitude gets to everyone's nerves. Even though Naoto's like that, Hajime still has his eyes on him. But, the problem is, Naoto hates homosexuals, so much that he wishes they will become extinct and rot in hell!!

3) All About My Brother
3.5) All About My Big Brother (extra)

Shinji has always loved his younger brother, Haruki more than any older brother should. Yet when he receives an unexpected warning letter demanding payment on a delinquent loan, he is left speechless. With everything Haruki could ever ask for, provided by loving parents, he demands to know what it could be that would cause Haruki to be so greedy and so irresponsible. Can Shinji really handle the truth behind Haruki's unusually selfish actions? or will he give up on Haruki all together?

4) Piano Lesson
5) Piano Lesson 2
5.5) Piano Lesson Variation (extra)

After his parents divorce, Hara Shuuji left Tokyo to live with his mother and attend the local school. With hopes of starting a new and peaceful school life Shuuji feels at ease when his first day starts out well. That is until a problem arises, a problem named Yoshie Kennichi, who carries the name of a "delinquent" with pride. Shuuji's first impression of Yoshie isn't good, but what's worse, is that his ideals for a peaceful school life are ruined when Yoshie suddenly recognizes him! Shuuji, a new student, has no idea how Yoshie can possible know him and frantically wonders, what in the world is going on!?

Shuu Kaidou is sent away to an all boys boarding school with a very strange rule: half the students must take turns to dress as girls!

A parody of the manga Naruto written by one of Kishimoto's assistants. Rock Lee's Springtime of Youth focuses on the strange antics of Team Guy as they work on becoming great ninjas, a job which often requires saving Lee from himself!

This story takes place in a world where humans and Vampires co-exist, and in a school that trains promising new vampires to help police their own kind. Unfortunately, the moon is separating, a bad omen in anyone's book! Enter Aldred, his team and the new human arrival, Kei. When vampires turn against vampires, how can they stop it?

Professor Kawato is the new Japanese teacher in the ill-famed Futagotamaga high school, whose baseball club is composed by thugs and bullies who have been suspended for a year from all school competitions, for causing a brawl during an official match. Now that the suspension is over, the only club members left are only interested in women, smoking and doing nothing until, under professor Kawato guidance, they discover a new dream called Koshien. However, the road to Koshien is far from easy as many obstacles awaits them

A sci-fi story set in a future where men have died off. Women have been divided into two groups: Adams and Eves. Each has a set role in society. The protagonist, an Adam, has just entered Kingdom Academy. Romantic relationships between Adams are forbidden there, so I'm sure you can all guess where this is going...

After a traumatic incident, Jun Sakurada refuses to interact with the outside world and return to school--he even shuts out his sister, his closest friend. Jun spends most of his time online buying spiritual items that are obvious rip-offs. One day he finds a website that curiously enough asks him to put his order in his desk drawer. Thinking it's a joke, Jun plays along. The following day a suitcase arrives containing a doll named Shinku... that comes to life before his very eyes! Welcome to the world of Rozen Maiden, where Jun must enter an all-new reality to protect and serve a living doll...

From Attractive Fascinante:

Rutta changed from a delinquent to a nice guy because of his new roommate, Miyagi Kodama. Kodama was unsure of his own feelings after Rutta’s confession. After seeing Rutta’s injuries caused from excessive fighting, Kodama finally decided to face the truth and accepted him.

Bi-Kwang is a handsome young warrior who becomes a drooling mess whenever he sees a pretty girl. Out on the road he meets an extraordinary swordfighter with no name who is searching for a legendary master warrior. Bi-Kwang promises to aid the swordfighter if he lets Bi-Kwang meet his beautiful sister. Of course, it turns out the swordfighter is the sister, Hwa-Rin Dahm, and she must switch identities to keep the plot moving along. Bi-Kwang is immediately smitten, and thus we have a triangle involving only two people.

This manhwa was made into a MMORPG.

Teenage Shakuya, the next head of the Dragon Clan, suddenly finds herself with two fiancés! The first vanished years ago but has now mysteriously returned. But betrothed number two is not about to just step aside. What's a girl to do? Her mother decides that at the end of a year, Shakuya will marry the man she has the strongest feelings for. How that will be determined is by "magic tattoos" on both of Shakuya's hands, each representing one of her suitors. As her love grows, so do the tattoos! And complicating all of this is that fact that whenever Shakuya gets upset, she turns into a fearsome dragon!

A salaryman Matsumaru Fumihiko 26, asked his colleague miss Tanaka to watch a movie with him, but she doesn\'t show up at the movie theater. As he is about to throw away the ticket, a rookie seiyuu girl named Onda Aka aged 20 asked for the ticket and they end up watching the movie together. On their way home they notice that they live near each other. That night, Aka\'s apartment burns down. Matsumaru offers his help and they end up with Aka living with him. They have to keep it a secret to secure their jobs. What will happen to the relationship that is more than friends but less than lovers

Motoba Hitachi has lived a boring high school life, until his kouhai invited him to a real-life simulation event of Incubate Castle, an online game they both played. But, what seemed like a harmless replication of the game turned out to be as real as it could get. Now, Hitachi must find allies to get out and survive this reality of a game.

There's a game going around Japan called 'Rabbit Doubt'. The premise of the game is that all of the players are rabbits in a colony, and one amongst them is randomly chosen to be a wolf that infiltrated the group of rabbits. Every round, the wolf kills off a rabbit, and every round, the group tries to figure out which of the rabbits is actually a wolf in disguise. Sometimes the kids who play this game decide to meet up in person, and Yuu, Mitsuki, Rei, Hajime, Eiji, and Haruka have done just that. Unfortunately, one of them has decided to take on the mantle of the wolf and has already killed once. Who is the wolf, and can they be stopped before everyone meets a very unpleasant end?

Sequal: http://www.mangatank.com/manga/judge-tonogai-yoshiki

Tsubasa, a normal teenage girl, promises to her dying grandfather that she'd fufill his last wish. However, it turns out that she must marry the heir of a tea ceremony school due to her grandfather's promise? What?! But, there are two heirs, so she must decide who to marry, or if to just run away from her problem.

From: Easy Going Scans

Officer Park Yoon Hee is a beautiful young detective who has high hopes of being accepted in the Violent Crime Division. However, her father and chief of police, has other plans for her… so instead of the Violent Crime Division he assigns her on the Unsolved Crime Division were nothing ever gets done and there is only 2 staff members including her!
The excitement that she most eagerly longs for though, is about to barge in her life when she will meet a mysterious boy…

Original webcomic