Despite his constant anemia, an accident leaves Akagawa Touma infested with an alien blood parasite, and the unintentional protector of Earth.

High school girls suddenly being falling from the sky over Tokyo, attacking and converting anyone nearby into high school girls. They survive all forms of attack and without a means to fight back the human population is steadily decreasing. Who's left to help save Tokyo?

From Tapastic

Vance just wanted to make the most out of his college experience under an authoritarian regime, and if that meant hacking into the university to assign himself a hot female roommate, then so be it. The last thing he expected was to be dragged into a crazy conspiracy to overthrow the government by his most-definitely-not-female roommate. College was meant to be exciting, but not this exciting. Between failed dates, failed grades, and successful hacks, Vance will slowly begin to question the morality of his actions and the true price of freedom.

Clumsy Arashiyama is a girl with a love for mysteries and a knack for getting into trouble. She works for an old lady’s lackluster maid café in a small shopping district. The cafe is largely unsuccessful in attracting customers aside from Sanada, a regular and one of Arashiyama's classmates (who has a secret crush on her). One day Arashiyama’s clever friend Tatsuno is invited to the café, and, upon seeing the miserable state of things (and Sanada, whom she has a secret crush on), decides to work there. Don’t miss the crazy antics of Arashiyama and friends, mismatched love stories, and all the hilarity that is created as a result, in Sore Machi.

From MangaHelpers:
There is a magic love app that supposedly helps people's dreams of love come true. The first story of this love app follows Tetta and Ginko, friends who have bickered since grade school. Tetta looks up the magic app on a whim, and ends up with an application that is connected to Ginko. When he manipulates the "Ginko" on the app, it affects the real girl. He's embarrassed to have it in the first place, but he can't uninstall it without inputting Ginko's measurements. Whether he actually likes Ginko romantically or not, it seems that this app could only make the situation worse.

Welcome to the future of vast bio-constructed cities with crime so severe that the cops drive tanks! For top tank-cop Leona Ozaki (and her trusty tank, Bonaparte), the day-to-day is a tall order already, but when the villainous and sexy (and super-powered androids!) Puma sisters become duly deputized officers of the law and are assigned to "help" Leona catch Urushi-Maru, "The Skyscraper Pirate," things are bound to get out of hand, especially in the midst of a full-on, tank-on-tank streetfight between Leona and a corrupt arms manufacturer bent on getting the city's police tank contract!

The story could basically be split into two halves. The main story is about Tamai Shiina, who is an energetic middle-school teenage girl. She visits her grandparent's over the summer where she runs into a very strange creature. Shiina has had lots of strange dreams as of late and also when she was younger, and this strange creature is somewhat related to her visions. She names the small cuddly star-shaped creature, Hoshimaru.

Little did she know that this cuddly creature is really part of herself. After her vacation, Shiina goes back to her home, living with her father. She runs into other children with similar creatures the following days. However, these children have developed their creatures, and they have complete control over them. They mostly use these creatures for their own destructive pleasure and not for good. There is a group of teenagers that all have these strange creatures, and they plan to basically conquer the world, creating a utopia of whatever they desire. Will they succeed? Will Shiina ever develop Hoshimaru?

Desperation leads humanity to eternal life, but will they be able to harvest its power? Or will it eventually lead to their end.

Humanity has long sought to discover the secrets of eternal life. Many have suffered and died in search of the legendary "Fountain of Youth," but none have succeeded on Earth. The answer comes unexpectedly when humanity is forced into space when Earth becomes imminently inhabitable.

Blood Ocean is a story based in the Pioneering Age of Space. War between the Federation and the Colonies plagues the galaxy as each fight to claim the Colquitt as their own. In the midst of the disaster, conspiracies and plot twists are revealed.

A story that follows the titular character's work as a private secretary. With Tanaka's support, a company can become invincible and achieve any future it desires.

A a variety of oneshot stories related to the supposed end of the world in 2012.

5) Nature-0 by HEE-JUNG Baek
Resource depletion, environmental contamination, desertification, and foolish wars. Mankind willingly walked along the path of annihilation. And at the end of that path, those who survived relied on the power of science and conducted endless experiments to obtain the valuable source of life. As scientists are exploring the desert's fallout areas, a child-like being is found naked on the ground and was brought into an underground survival refuge. As they analyze the child, what will they discover?

8) Myum-Myum by currygom
The world is in an uproar over the discovery of a stone tablet thought to have been created 500 years ago.
The stone contains predictions of major incidents that happened worldwide in the last 500 years. All of its prophecies had already come true. There is only one prophecy recorded on the stone that pertains to the future ahead: that the world will end in a year?s time, and only those who believe in the god drawn on the stone will find salvation.
The name of this god is... Myum-Myum.

13) If the World Ends, That's Cool! by Rangto
Friday the 24th, August 2012.
The world will end due to a meteorite crash... tomorrow. But people are fine with it. No one is screaming. No one is praying. Because they are all... cool.

The fabulously creepy story of The Ring takes a side step from the plot of the original Japanese film, taking the reader into life after all that tragedy and mystery. And guess what? Sadako, the psychic killer, isn't so easily disposed of.

In U.C. 0093, Char Aznable returns as leader of Neo Zeon, and is determined to drop the asteroid base Axis on Earth. Opposing him is the task-force Londo Bell, led by Amuro Ray and his Gundam. The final battle will take place over the Earth Sphere.

High above Farmless City, citizens are stunned by the sudden appearance of two floating figures. Are they human boys, monolithic robots, or something much more strange? As the battle ensues between them, destruction and devastation falls on the hapless city. One figure is Vice, and seems to be as evil as his name implies. The other is Ultimo, intent on trying to stop Vice from wreaking more havoc. But who are Vice and Ultimo really? Where did they come from? A new mystery begins with the fate of the world possibly hanging in the balance!

As Shin Youngwoo has had an unfortunate life and is now stuck carrying bricks on construction sites. He even had to do labor in the VR game, Satisfy!

However, luck would soon enter his hopeless life. His character, ‘Grid’, would discover the Northern End Cave for a quest, and in that place, he would find ‘Pagma’s Rare Book’ and become a legendary class player…

A short taken from an Enomoto Shunji tribute collection.

“We are the beautiful Sexy☆Socks! The ones who eradicate evils and preserve hope!!” To protect the city from the attacking ‘monsters’, five girls come to the rescue! Sexy Blue (Nanako) is being protected by Sexy Red (Kanata) as they face powerful monsters. However, for the first time, they encounter a monster which takes a humanoid form…

About a dream handler, and the decision he takes for the sake of his client.

The number of humans has plummeted in a world where a deadly poison was spread by the explosion of a research facility. One day, Professor Murase discovers a girl who was preserved by a capsule. In a world where there are no young women, her existence has become the saving grace of humanity.

Civilization is dead, but Chito and Yuuri are still alive. So they hop aboard their beloved Kettenkrad motorbike and aimlessly wander the ruins of the world they once knew. Day after hopeless day, they look for their next meal and fuel for their ride. But as long as the two are together, even an existence as bleak as theirs has a ray or two of sunshine in it, whether they're sucking down their fill of soup or hunting for machine parts to tinker with. For two girls in a world full of nothing, the experiences and feelings the two share give them something to live for...