In recent years, more and more girls are experiencing the development of "tertiary sexual characteristics" during the later years of their puberty -- that is, the rapid masculinization of a certain part of their external genitalia. Ooi Haruka is one such girl, who has until now kept the changes in her body a secret from everyone but her family. However, after an embarassing incident involving the guy she's been crushing on in a crowded train, she wakes up to discover herself at school, surrounded by a group of students calling themselves the "Bra Girls (Swing Girls)." And they know her secret!?

Boys Be... (ボーイズ・ビー Bōizu Bī) is a manga created and written by Masahiro Itabashi and illustrated by Hiroyuki Tamakoshi. Three different Boys Be... manga series were serialized by Kodansha in Shukan Shōnen Magazine. In 2009 Kodansha announced a fourth series, Boys Be... Next Season, starting in the November 2009 issue of Magazine Special.

From Tokyopop:

An anthology of stories about ordinary high school guys and their relationships...or lack thereof. Boys Be...takes a look at the trials of love and loss from a refreshing point of view and often adds interesting insight into what a relationship is like from an average guys point of view!

After her grandfather's death, Mikura chose to continue their island express courier service. With her seaplane and her adventurous cat, Endeavor, she lives life as she chooses. Soon, Mikura becomes very interested in a mysterious island that seems to move around, according to local legend. After some extensive effort to determine the island's whereabouts, she manages to get a brief glimpse of it from the sky. Now that she knows it's real, she's determined to find the island again, no matter what it takes!

Homura Tsukishima and Sakurako Hirosue are roommates at Principia Academy, a school located on an island created specifically for researching "shiki", which is a form of power created by manipulating numbers.

Ginta's father works at a cellphone company called "Choto Bank." Their new cellphone is a humanoid cellphone. Gina's father sent his son a prototype version of the humanoid cellphone, but Ginta's sister unexpectedly made some "changes" to the new cellphone and due to that it makes countless mistakes. The cellphone humanoid, named Momoko, slips on flat surfaces, rips Ginta's jacket, turns a jacket into a puzzle, and trips and nearly kills Ginta when a pair of scissors slip out of her hand. Ginta asks himself, "Will I live long in this condition?"
{Notice: This manga is different from traditional manga. Instead of reading right to left, it reads left to right.}

The Otohime Private All-Girls High School is a very prestigious school and full of pretty girls. However, there is one male student attending the school, the director’s son Ouji. Ouji is a creepy pervert who can get away with anything because his father doesn’t punish him. He’s got video cameras all over the school to get footage of his classmates naked or near-naked and constantly sneaks around with cameras to get photos of them. The school is his paradise.
All this will change in the coming year, though. His father has decided to make the school co-ed, but with only baseball players so that they can aim for winning the National High School Baseball Championship at Koshien Stadium. In preparation for this grand dream, the director insists that the girls of the school establish a cheerleading squad. Seeing his glorious world collapsing around him, Ouji latches on to the most hopeful thing he can find: the cheerleading squad. Now he and the reluctant student council president, Itsuki, are going to recruit members and try to get this team going.

After being the only survivor in a plane crash and losing his parents Ryouga, a young boy, is troubled by nightmares and taunted by other kids at his school. Fed up, he agrees to transfer to another school intrigued by a mysterious offer and the hope they may know why or how he was able to survive the crash. Arriving at the new school, he learns he must play a little card game with three others before being accepted... one card each, one vicious monster each, gruesome deaths for all save one.

Kisaragi Maki is the heiress of a yakuza group. She only dreams about being a normal high school student, and becoming an ordinary bride. However, when she sees blood, she changes completely and becomes violent. Will she be able to keep living an ordinary life?

New dawn of historical gunfights! A Meiji Era like no one has ever seen before is here!

Akabane accidentally discovers that his classmate Sumomo is one of the Japafive Rangers. He is then recruited as one of the Japafive Rangers but things don't go very smoothly.

It's not serious, feels more like a gag parody more than anything else

An alternate Code Geass story in which Lelouch's fate is unknown after his meeting with C.C., whether he be dead or alive. Nunnally makes a Geass contract and gains the power to read the lines of the future. She also obtains a new body and takes up piloting an unusual Knightmare Frame.

It happened after school one rainy day... A group of friends have stayed behind to prepare for the next day’s school festival. One moment they are idly telling ghost stories but the next an enormous earthquake strikes and the entire school seems to fall down around them. They awake to find themselves trapped in a parallel version of their school. A school abandoned and disheveled and whose calendar dates back to 1927. Can they find a way out of this nightmare or are they doomed to the same fate that befell the other victims whose corpses that lie numerous throughout the school?

From Manga-Heaven:
Long ago, a devil traversed the world leaving nothing but death in his wake. Eventually the demon was slain by the 10 gods who created the world. As the people began to worship the gods, the gods created 10 swords infused with their power to protect the world from evil and peace dawned upon the world once more...
Mirim is a member of the 10 Pillars Sword Guild and one of its elite earning the title of Crimson and the right to wield one of the swords forged by the Gods. Her companion, Ash Grave, is the devil of legend. Why is a swordswoman with divine power to protect the world paired with the demon that is said to be destroying it? Perhaps there is more to this legend than meets the eye...

The people of Earth live in a society where vampires aren’t just real but dangerous. Although humanity has been able to keep them under control and even take the night away as the vampire’s natural habitat, some of them have adapted. Hesperides, a relatively new breed of vampires, have adapted over hundreds of years in order to be able to go outside during dusk when the sunlight is at its weakest and feast on humans. Aburaya Shiro, a high school kid, lives in a town where there has not been a vampire attack in years, but adults keep warning them of going outside at dusk. Shiro and his classmates take this warning lightly and head out at dusk only to find out one of their classmates who they thought they knew well turnz out to be a Hesperides. With all his classmates violently murdered, the only way Shiro was able to survive was with the help of a different classmate, Ichijoji Eruka, who doesn’t seem to be human herself.

Kasuga Rito had a hidden wish for a very long time: to use his ability for good and to help people. But before he could do that, he needed to gain the power of magic first.

Rito is a sophomore in Rezon Institute, a school for people with special magic abilities to find, train, and develop their skills. Each student has to reach 100 points to be able to start using their ability. Otherwise they won't move up from the "Common" and into the "Starlight" class. But Rito, known as "the Eternal 99", has been stuck with an unchanging 99 points for a long time.

So here comes his new plan: to become a friend with Scuse Fontana, a three-day exchange student from the Demon World, and to ask her for some food. (There's rumor that a human can increase his power by eating food from the Demon World). He slipped into the hotel where a welcome party is being held for the much respected lady, just to find that she's actually absent. Losing hope, he wastes no time leaving the hotel. At the back alley behind the hotel, he finds a tiny dragon, which for some reason sticks to his head and now he can't get it off...

When a person who under goes extreme depression/anxiety, loses control, a person will become a demon consumed by darkness. Luckily there are those devoted to hunting those demons.
Boy meets monster while taking shortcut home from school, is rescued by a girl with a gun. Monster gets away. Later on, girl makes contract with boy and uses his soul energy to make a big gun and kill the monster.

Ninomae Iko, has lived in a house of only her dad and brothers, who all practice kendo. Looking to become a little more girly, she transferred to an all girls' school. Here, rumor has it, a magical cup filled with red wine will grant any wish if your blood is dropped into it.

Note: Plenty of pantsu moments.

In the midst of a terrorist attack that kills all his classmates,Tohru Kuroe knows the chances of seeing yet another woman die makes Tohru pick up an abandoned gun - The beast awakens; taking over. When Tohru comes to his senses, he finds he is now a killer. Finding out he was genetically engineered to be a killer, his codename is D-17, Tohru continues his 'normal' life amidst challengers threatening his life and those around him.

From Horobi no Michi:

Clockworkers- mechanical men, created during the war as a weapon to kill as many as possible. That war may be long over, but rogue Clockworkers are still roaming about, spreading fear and death wherever they go.

Machina's a member of the CWA, an organization dedicated to the destruction of these rogue robots.

Along with Deus, her Clockworker partner, she travels the country in pursuit of these dangerous robots...