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.

Comedy about a high school manga club. A frog god who can turn into a good looking guy lives in the club meeting room, but that has very little to do with the plot. He's there to just read manga.

From Awakened Memories: The new school Lilia has just transferred to has a lot of people with suspicious abilities. There are vampires with fangs and the snow woman's son. And then it turns out that Lilia herself is a demon who sucks the life out of men by kissing them!?

From BLU comes an unearthly collection of stories illuminating the complex lives of immortal beings. An angel, who loses his place in Eden, finds a mysterious and dangerous new patron. A poor painter finishes a woman's portrait without a subject and reveals his forgotten past. These stories and more will delight fans of beautiful angels and demon boys!

From GOoC:
Data is a kind of Magical Boy series manga by Tachibana Kaimu. The two main characters, Sakura and Yuki, are on quests to gather stones with magical powers. In doing so they are also hoping to uncover the mystery as to why they both seem to have lost their memory. A lot of new characters who are also "hosts" for the stones join in the fun as the story progresses.

The lord of darkness has decided to wake up the Dragon God that will give him the necessary power to dominate the world. But the Dragon God doesn't like his intentions and decides to entrust the mission to find the element that will revive him to the human who holds his soul.

Sequel(?): 팔용신전설 Plus

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.

Monsters descended upon the humans all of a sudden, monsters that can't be detected by most, unless they have a strong sense. An invisible predator, it feasts on humans to grow in strength and powers. 4 Death Gods are chosen to destroy these monsters and to seal the "sink" hiding the monsters fast.

While Japan in desperate situation, 13 "devil survivors" cut deals with devils to obtain abilities to fight against unknown invaders with only 7 days left until a world catastrophe, you need to make crucial decision to survive...

Kinda creepy. Dante, the main character, is fighting various characters to keep the passage to the demon world sealed, but he doesn't seem to be having much luck... (And the story says 'To be continued' at the end, so there might be more to it.)

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...

Kenichi is a high school guy who wakes up in a magical land. Together with a fairy and a swordsman, he must recover two magical items to save the magical world as well as his own.

note: The manga has been reprinted in a normal tankoubon size with only Akiyama Tamayo noted as author.

Republic of Biscotti faces a predicament by the invasion of Galette Leo Knights. In order to save the country, Princess Milchore summons a "hero" from the outer world. Shinku, a junior high school boy living in the Earth, is chosen as the hero.

*This series contain side stories to the anime series that take place before the series, in between some episodes and at the end.*

DOCTOR! is a manga by Ippongi Bang staring the mysterious young Doctor (Yeah, that's his name) in a fantasy world taking place in Latin America.The art of surgery has been lost, and illnesses are caused by demons and forces of Darkness. Doctor travels with this little blob named Liquido Medio and they travel around from place to place curing and helping people along the way.

From Transcendence:

This is a tale full of wonderful Ancient Chinese legends. A group of beautiful female fox demons lived at the base of a mystical mountain. Among these foxes is the very special Caisheng, a little fox girl with the ability to change into a male fox demon when she matures and allow the continuation of her species. One day, she secretly went into a nearby human village and befriended a boy named Duoxi and a girl named Xiaoque, and when the little fox child is attacked by a dog, the two human children saved her! Now the two children are marked, and will remain so -- even in their reincarnated lives -- until Caisheng repays her debt to them...

Two hundred years later, Caisheng not only becomes the most powerful fox demon but also has mastered the art of gender transformation. She begins her search for her saviors' reincarnations: the boy now known as Yunshi, and the girl as Ping'er. Not knowing Caisheng's true identity, Yunshi falls in love with the female Caisheng, and Ping'er with the male Caisheng! But Yunshi is a priest whose duty is to destroy all of the demons... what will he do when he discovers Caisheng's true nature? And whom will Caisheng choose in the end?

(Clarifying note: Very low smut content)

Ten thousand years ago, a great and powerful Digimon was defeated and sealed away by the Holy Knights as the "Digi Core". Years later, a virus infected the digital world, leaving only those that possessed the D-Antibody (X-Antibody) remaining. The only members of the Holy Knights remaining are Omega of Power (Omnimon X), Duke of Courage (MedievalGallantmon/Gallantmon X), and Magna of Miracles (Magnamon). At the start of the series, the "God of Death" MetalPhantomon draws Hikaru, Kiyoshi, Masuken, and Teru into the digital world. Originally, Hikaru is left alone with his Digimon (which starts out as a Dorimon), and has to battle his friends Teru and Masuken, who are under MetalPhantomon's control. At one point, MetalPhantomon steals the "Dragon Spirit" of Masaru's partner, who is now a Dorumon. While MetalPhantomon uses it to revive the Digi-Core, Hikaru, Teru, and Masuken learn from Omega of Power that they can get a new Dragon Spirit from Duke of Courage - with this, they can save Dorumon's life. But when they arrive in Duke's area of the Digital World, they are given a series of tests by Duke's servant, MameTyramon. After completing the tests and battling Duke himself, they manage to earn Dorumon a new Dragon Spirit. However, now they must battle MetalPhantomon, who has resurrected the Digi-Core as Dexmon. In the end, Hikaru and the others manage to save their friend Kiyoshi, who was sealed inside Dexmon, and return to the real world.

V-Tamer is a manga version of Digimon that was never really released in English, but various sites have talented people who have actually posted a translated version of this great series. Based on the original Digimon V-pets, V-Tamer certainly brings a whole new twist on the world of Digimon. It opens with Taichi, the main character of the series, attempting to enter a tournment with his V-pet, only to be disqualified because the monster on his V-pet cannot be identified and therefore was not a Digimon that was supposed to be programmed into the V-pet.

A short time later, Taichi finds himself in the Digital World and meets up with his Digimon, Zeromaru, or just Zero for short. Zero is a V-dramon (Veedramon), and between himself and Taichi, they have a battle record of 100%. For this reason, the two of them were chosen by Holy Angemon to save the Digital World from the supreme evil, Arca Demon. With the help of their guide, Gabo, Taichi and Zero set off to defend the Digital World from Arca Demon.

From Friendship Scans:

Ke Lin received a doll with the same name as her as a present from her dad, who found it on a business trip in Germany. When she took her new doll to go play at the park, she met and became best friend with a boy at the park.

However, he had to move away soon and so, he made a promise with her that he will come back and find her. She gave him one of the glass shoes tied with a ribbon from her doll with her name on it as something to remember her by. Every day, she comes to the park waiting for him…believing that he would come see her again.

Fast forward to a few years later, Ke Lin is now a high-hchool student. QiangShu is a one of the students from the same high school. Ke Lin is attracted to QiangShu and reminded her so much of that boy from her childhood. However, there is a big problem – QiangShu is a GIRL!?

Second part of the Agreement of the Glass Shoe trilogy.

From Aerandria Scans:

It starts with poisonous herbs under the cradle. Then under the sheets. And inside the clothes. Even mixed in the milk that they feed the newborn. This way the child gradually gets used to poisons and becomes the perfect assassination tool - the “Poison Princess” whose every kiss, tear, and even touch bring death. Her only chance of survival is to fulfill her duty as an assassin and find a way to live on in the enemy land she is sent to…if her heart is strong enough.