Aiko should be dead, but when she awakes in a secret hospital, she has no recollection of what happened that night. Until a monster showed up and her memories flood back. Her arm changed into a powerful weapon similar to the monster, a chimera arm.

The secret organization Atheos asked her to help them fight off the chimeras. An accident happened that led Aiko to understand how much she wants to live, and decided to join Atheos, in order to find her place.

From: Easy Going Scans

The prince of Szak territory, Iska, was misled and inadvertently released an ancient monster, Nue, while stealing the katana that had sealed it for 400 years! And the first victim of the monster is Iska's own father!

Because of his act, Iska is also cursed by an evil power… In order to make up for his mistake, he will embark on a dangerous journey with the stolen katana, chasing Nue to the end of the world to make him pay for his sins.

The legend tell that the only weapon that can kill Nue is the famous katana “Yukihira” which was manufactured by a demon of the Temma clan. Iska will try to find their village in order to learn more about Nue…

Note: This was originally published in French, hence the category Manfra below.

Nina, a wyndian princess, and her guardian Cray are searching everywhere for Nina's missing elder sister, Elina. While traveling to her last known whereabouts they suffer an accident. On her way to a nearby town, Nina meets Ryu, a seemingly amnesiac young man. This meeting triggers a series of events that will involve them with the godly race known as The Endless, immortal dragons with the power to shape the world itself.

Closely follows the storyline of the original game.

A high-tech adventure set in a digital world. Sam Flynn, when he was a child, has been told stories about a different world his father created. After 25 years of not seeing seeing his father, he enters his dad's arcade and finds himself pulled into the digital world of "TRON" where his father has been trapped and living for years. This is a life-and-death journey of an escape across a cyber universe that has become far more advanced and exceedingly dangerous.

Based on a movie

From Mango Scans:

The world is completely changed when “Sacred King”, the military satellite created by the scientist Arthur, loses control. Arthur’s personal army, the “Trance Knights” have broken up, and other organisations are attempting to take control of the satellite. In the midst of these events, Arthur’s daughter Ley, who holds the key to the “Sacred King”, encounters Gawain, one of Arthur’s former knights.

From Hyper Parfait:

After World War III, the Führer established the Unified World Government. Anything considered as damaging to the creation of the “Perfect World” is eliminated, such as people with disabilities, believers of a different religion, those that are considered as “traitors”, and so on.

The Black Rose is the personal protection guard unit of the Führer. Luka Ogami, the top graduate of the academy of unified army officers, joins the Black Rose…. to save the world.

One of the manga that take place in the Touhou series (mainly known for the games by Team Shanghai Alice)

Based on a novel by Wada Ryou, Shinobi no Kuni brings a story that blends history and fiction as it shows the struggles happening during the 16th century in Iga, a region famous by the Iga Shinobi, the Dragonborns.

The continent of Halkeginia is tumultuous--a place where the various kingdoms, princedoms, dukedoms, and fiefdoms strive against each other to expand their domains. They nobility scheme and plot among themselves to gain influence to their lieges or to even foreign lieges. In the middle of Halkeginia is the small but important kingdom of Tristein. The most notable fact about this kingdom is the Tristein Academy of Magic where nobility from all over the world come to study magic so they can become magi. Although friendships will form across national boundaries at this school, will they survive the politics and games of the world at large once they leave?

Louise is a student at Tristein Magical Academy. She is known to be quite a screw up when it comes to her magic. One day, a ceremony takes place where each student is to call forth a being or entity that will become his or her familiar. For Louise, her familiar comes in the form of a boy named Hiraga Saito. Somehow, he managed to get transported from his world into hers, and shortly after became her familiar.

From Infinity Studios: Having been born in a secret government laboratory that cultivated esper (telepathic) powers within humans, Shuuichi and two sisters, Sumire and Katsumi, are forced to endure a difficult life as test subjects until their escape. Years later, these siblings are still being sought after by unknown organizations that are after Shuuichi powers as he is what they refer to as the “zero-sample” with the ability to cause “zero-shock.” Scanlated by Helz0ne http://helz0ne.zone-anime.com

Daisuke Aurora works with the special division of peacekeepers in the city of Jewde, one of the largest cities on the planet. He and his android partner, Heat Guy J, team up to make sure that anything illegal stays off the streets and out of circulation.
However, their presence doesn't sit too well with the local mob leader--a ruthless, unbalanced, well-armed son of the late Don, who is out to prove that he is not too young to take over the family business. In the city that never sleeps, will Daisuke and Heat Guy J end up sleeping with the fishes?

Yugo Beppu is a master negotiator and mediator. Fluency in five languages, Socratic wit, and a deep understanding of human nature combined with top-level international connections make him a formidable operator. When a woman's father is seized by Dacoit bandits in Pakistan, Mayuko seeks Yugo's help. After complex and dangerous negotiations, he secures his release. After this success Yugo is called in to deal with yakuza in Japan, triads in Hong Kong, the IRA in Northern Ireland, and the Russian Ministry of Internal Affairs in Siberia.

Note: New versions of this manga were published under different arcs in bunko format such as the Pakistan Hen, Russia Hen, etc.

From Aerandria Scans:

In a time when there were swords with spirits dwelling in them, there was a warrior named Hisui with a “Drunken Sword.” With the emperor ordering people to gather these Spirit Swords for him, Hisui spends his every day fighting assassins sent by the emperor and freelance Spirit Swords Hunters who simply want the reward money, all the while protecting his beloved childhood friend, Shirei. However, Shirei might not be what she seems to be...

From: Easy Going Scans
High-school student Jinpachi Kogure is a member of the manga club and is no good with women. Yumika Testuyoshi is a troubled female high-school student who's always skipping school and searching for a girl she doesn't hate. However, these two are in reality young masters of the art of killing people:"Young Guns.

The shogunate installed by the Tokugawa is abiding order, the people live in peace and in a relative prosperity.

However, the dark part of the human heart does not cease to arouse their cupidity : it is the ideal doorway for all demons that, by possessing humans, seek to pass into their world.

Exorcising these demons is Jonosuke's mission, the master of keys. Known for being the best locksmith of Edo, Jonosuke uses particular locks to put the wicked spirits under lock and key. With the help of the bewitching O-kin, a divine who uses unorthodox methods, Jonosuke is going to meet during his demon hunt some notables of his time, who will prove to be precious allies when he faces a plot aimed at the upper spheres of State.

Ashihara Chihiro is a regular high school student. One day a man came to her and told her that she's actually a princess from another country in another dimension. Chihiro later found out that it was true, and in fact her own best friend and teacher were actually her guardians! Her country has been taken over by Raja, who is now king. Chihiro and her guardians come back to that dimension to take back their country. In her quest, Chihiro met other guardians and warriors who were willing to help her achieve her goal.

Yoshiaki is entering a school that is famous for its fights and violence. He chose to go there for just that reason, and he intends to be the strongest one there. When he first arrives, he helps out a girl called Homura, who is being picked on by some guys. When she asks him to be her "sword" afterward, Yoshiaki doesn't know how to respond. Apparently, students of the school team up in pairs; a "sword" and a "master". Others advise him not to associate with the girl, who is a "Rank F", as she probably won't live very long. However, Yoshiake is not thrilled with the idea of abandoning her to die.

In a post-apocalyptic world covered with water, Wadatsumi, a person who lives in what appears to be the last piece of land, finds a mysterious girl dragged by the waves of the sea. Where does she come from? Are there other lands in this world?

From Taruby:
After 'The Great Sinking,' civilization on Earth crumbled as the world was drowned in the ocean. One tiny band of survivors eke out a living atop the ruined remains of a skyscraper. Wadatsumi, a young tomboy, is saddled with the care of four elderly gentlemen, until a chance encounter with a group of pirates and a mysterious woman turn her world upside-down.

High-school student Kisaragi Maki has one dream: to be a normal wife. She’s part of a Yakuza family known as Group Kisaragi and her father is the third generation of the group - and he wants Maki to be the fourth generation! But Maki isn’t a ‘normal high school student’. She has a split personality which gets her into all sorts of trouble. Can Maki achieve her dream of being a ‘normal wife’?

A Spin-off of Hitman Reborn.