From MangaHelpers:
Before they enter high school, the boys Meguru and Shou are whining about the fact that neither of them has a girlfriend. A strange, large-breasted woman shows up, claiming that she will fix their problem, and kisses Meguru. This odd occurrence is pushed out of the boys' minds when they meet up with Souko, a friend from elementary school, who is going to be in their high school. She's grown up into a pretty young girl, and it seems like the boys might have a shot with her!
That evening, Meguru realizes that the strange kiss may have had more meaning than he thought: he's turned into a girl! He convinces Shou and his mother of his identity, but no one has any idea how to turn him back. Now he's going to have to learn how to be a girl and let go of his hope of dating his cute childhood friend Souko. What will happen to his hopes for a popular high-school life?

A story about a demon hunter named Rano who is trying to find his sister. Along the way he finds a person who has the same teeth structures as demons yet is not affected by sunlight. This person, Lessa, seems to remember who Rano is, but Rano does not remember who he is. Rano only dreams of this person; what are the connections between these two?

Three years ago, Karamura Neneko's father died. Since then, she's been living together with her older sister, Nanako. They've been living together happily until recently, when Nanako starts acting strangely. There will be nights that she doesn't sleep at home, and then one day she completely disappears. Not only that, but she quit her job at a company that she had been at for a long time.

Worried about her sister, she remembers a place that her father told her to go to if she was ever in trouble, the Raubritter. Upon arrival, she meets Shinobu and Yokana, cousins that run a detective agency, more-so as a hobby than a career. Since they are both fairly wealthy they never ask for payment. They only help young maidens in need, and since their business is a secret, only people with connections come to them. It turns out that Neneko's father helped them out a lot in the past. The cousins are heart broken to find out that he died, so they are more than willing to help Neneko find her sister.

What has happened to Neneko's sister? Will a special relationship develop between Neneko and the cousins?

From SCX-Scans:
Though it was a bit strange, three people ended up meeting. One, who looks younger than her age and able to see the supernatural. Another who is possessed by a "Yamanko" which refers to "Yama no ko", or a mountain child. She was possessed due to her bloodline and due to the possession, she has superhuman abilities which she can call upon. Finally, an awkward person who enjoys writing poems. Coincidentally, the three are also classmates.

Taken from the Holy Scriptures of the Old Church of Selakiel:
"When the Earth begins to perish, the Messiah will descend from the Heaven on wings of light. Clad in darkness, he will be so little yet he will be so immense surely he shall bring salvation to everyone."

"The four saints shall appear to offer him their assistance. One will give the Messiah courage, one will give the Messiah light, one will give him wings, and one will shield him from his enemies."

Note: Chapters are numbered differently starting on volume 7, since it's a beginning of a new arc

The manga is separated into 3 story arcs with close to none relation with each other's characters.
Volume 01-13: Video Girl Ai
Volume 14-15a: Video Girl Len
Volume 15b: Video Girl - Complete Story (about Video Girl Haruno)

Video Girl Ai [From Viz]:

High-school student Yota Moteuchi is so unpopular that his classmates have given him the nickname "Dateless." So it's no surprise when the love of his life, Moemi, is not interested in Yota but instead is in love with Yota's best friend, Takashi. Yota turns to a video rental shop for comfort, but little did he suspect that the shop was magical and that the cute girl on his rented tape would pop out of the television and try to fix his ruined love life!

From Aerandria Scans:
Our protagonist, Hikaru, is a member of the astronomy club at her school. On one beautiful starry night, she encounters a tall boy with blonde hair that looks almost white. However, he turns out to be...?!

1) Solely S, Absolutely M
Mamiya has gorgeous looks, terrific grades and outstanding sports reflexes. He’s very popular with the girls in his class, but seems to have no interest in them whatsoever. Sawako is the only girl who treats Mamiya like a slave. She thought there’d be no change in their relationship, but…!?

2) Jitter Bug
When Akane's mother died, she thought she was all alone in the world. Then she found out that her father is still alive and that she has three brothers. What will she do when she finds herself falling for her younger brother?

3) My Dear Cat
Hosoya Mizuki is a university student who has a boyfriend. One day on the way back from school she sees a beautiful cat with one blue eye and one brown eye which seems to mesmerize her. What will happen to poor Mizuki when she will meet a handsome guy with one blue eye and one brown eye and what about her boyfriend?

4) Bet!!
When she secretly took a picture of Saeki-kun, the no.1 popular guy on campus, she witnessed a scene she really wasn’t supposed to!? A bet has been made by him that if he can make her fall in love with him within a week, she'll have to delete that picture... who will win this bet?

5) Love Planetarium
Satoko Fukaya is heartbroken after being dumped by her boyfriend, because she was transferring to another school. While crying she is suddenly pulled into the planetarium by Nanasawa Kouki who seems to have taken an interest in her.

Extra) M's Dejection
Sawako continues to treat her boyfriend like her slave, resulting in Mamiya thinking about breaking up.

"To Hiiragi Kouichi-kun. I'll be waiting for you after school behind the school gym. Sakuragi Umeko." These were the words written in the first love letter Hiiragi ever received. But when he meets Sakuragi, she tells him that she wants to take him to the planet R'lyeh!?! Disappointed that the love letter from the cute girl came from a nutcase, Hiiragi returns home, only to find that Sakuragai won't give up so easily. Not only that, she may have been telling the truth afterall! But then again, Hiiragi isn't such a normal guy, either...

Randou Masashi, a self-centered, brash karate star, was the victim of a horrific bus accident that left him comatose, his face terribly disfigured by extensive burns.

Genius plastic surgeon Dr. Manabe saved Randou's life and went to work on his face, gradually reconstructing it based on a photograph found in the wreckage of the bus. But in a cruel twist of fate, the photo that the doctor used as his reference was not a picture of Randou, but of Rina Kurimi, the girl whom Randou has a crush on!

A series of interconnected romantic comedy one-shots involving a Royal Family with 7+ sons in line for the throne and the men they fall in love with. The series also occasionally chronicles the romances of other palace employees and secondary characters. 1) Prince vs Slave - The youngest (7th) prince Shuki, gets hugged by new slave, Fuanron, that seems to know young prince. Shuki starts to bully the slave till their roles get reversed and he even takes place of the prince's teacher, Riiren. Who is Fuanron in reality? 2) Prince vs Assassin - 1st prince, Ryuuen, gets attacked by Seiran, but he defeats him and makes a deal: the assassin can try to kill him all the time, but if he fails, then he must spend the night in the prince's embrace; and so starts Seiran's life as an official consort. 3) Right-handed Priest vs Left-handed Priest - Rei has been in love with Ryuuen (the 1st prince) for years and now he has finally become the minister of the right. He thinks he can get closer to the 1st prince, but there is an obstacle, the minster of the left, Rai, that says that he is in love with Ryuuen too. 4) Mercenary vs Prince (vs The 4th Gun-Warrior?!) - 6th prince, Kagetsu, fell in love in Jin, who helped him with his wounded feet. Now he escapes from the castle everyday to tell Jin that he loves him, but the mercenary doesn't believe him. Suzaku always comes to drag Kagetsu back to the castle, but what are his real motives? 5) Scramble Showdown (?) - Short comics (one page for each) with pairing: Jin x Ryuuen x Seiran, Rai x Seiran, Kagetsu x Fuanron x Shuki, Rei x Shuki (x Rai x Fuanron), Suzaku x Riiren x Tailor. This story of 2nd prince is also featured in the manga, Ousama Game. 王子様★ゲーム

A newly hired detective tries to prevent an infamous thief from blowing up a precious diamond.

Ten-year-old prodigy Negi Springfield, has just graduated from magic academy, and in order to become a master mage he is sent to Japan to teach English at an all-girls middle school. But Negi has a bigger dream than just becoming a master mage. He wants to find his missing father, "The Thousand Master", the strongest mage that has ever lived. And he soon finds that searching for his father wont be as easy as he first hoped. In fact, it pushes him and his students into life-or-death battles that decides the fate of millions.

A cat went in the hot-tempered KANG Jae-Young's villa.
Forbid approach to my room and my library.
Things must be always in place.
I hate messy things and clamor.
Just follow the rules!
Darn! >v<
I won't be daunted.
It's not like that I want to live passively and say no other words but "meow meow".
Seems to be acting modestly, and all of a sudden extrudes the claws while sounding "Grr.." like a wild cat.
Kya~!
Now can love be formed?!!
Let's wait and see.
The vicissitudinous cohabitation diary~

Recently rejected Saki Momota is having a hard time getting over her first love. While picking up her younger brother from school, Saki bumps into Akai Ryuuichi; the class delinquent who's rumored to be able to shoot laser-beams from his eyes. Could this day get any worse?

From DGT:
Yating was working in a recording company until she was fired by her boss (a famous movie actress with a spoiled temperament). Discouraged and jobless, Yating decided to work in a pub where a famous group called "Gangster" regularly played. Along the way, she gets to meet this guy who has the most divine voice. Yating's luck then began to change when her uncle decides to retire and set up his own record company. He asks her to join in his ambition to create the most famous rock group in Taiwan. This is the story of how Yating, being the new manager, tried to create the ultimate rock band!

Second-year culinary student Sakai has always dreamed of opening his own little restaurant and being able to touch people's hearts with his cooking like his grandfather did. Except he's at his limit, fainting in class from overwork and fatigue from commuting three hours every morning just to get to school but there's no way he can afford to live closer.... Until his classmate tells him about an almost too good to believe room share nearby. And so begins the story of four misfit roommates.

Sakura is the princess of Clow - and possessor of a mysterious, misunderstood power that promises to change the world. Syaoran is her childhood friend and leader of the archaeological dig that took his father's life. They reside in an alternate reality where whatever you least expect can happen - and does. When Sakura ventures to the dig site to declare her love for Syaoran, a puzzling symbol is uncovered - which triggers a remarkable quest. Now Syaoran embarks upon a desperate journey through other worlds - all in the name of saving Sakura.

Our hero Vash the Stampede disappeared for two years after blasting a crater onto the moon above the desert planet he saved from annihilation. But with good people and bad alike trying to track him down, he won't stay lost for long! Count on more crazy gunslinger action, new dastardly villains...and a new outfit, to boot! Nightow changed publishers to Shonen Gahosha and the series continued to be serialized in Young King Ours magazine. Due to the original publisher retaining the name Trigun, Nightow had to change the title to Trigun MAXIMUM, which isn't a sequel; just a new name for the rest of the same series.

Riding high on the memory of a boy named Hikaru with whom she spent a day during her last year of grade school, Megu went through middle school without romance. Now that she's a high school student, she has decided she is finally completely over her first love and can look towards the future. But! Megu meets a pretty girl on her first day of high school who gives her a big hug, and her name is Hikaru?!

Note: this manga is currently on hiatus due to its author's copyright infringement. There has been no notice since June 2012 about its re-appearance.