Nagai, Go

Soft-hearted Akira Fudou has always been somewhat of a pushover. When he reunites with his childhood friend, Ryou Asuka, in a fateful encounter, Ryou reveals to him the terrifying reality of his father's research: demons exist and are planning to claim possession of the earth once again.

Eager to help his friend save humanity, Akira agrees to attend Black Sabbath, a party filled with depravity and corruption, to attempt to merge with a demon. A near-death encounter causes him to unify with Amon, a demon feared amongst even his own kind. Together they form Devilman, a combination of Amon's strength and Akira's pure heart.

After uniting with Amon, Akira begins to fight against the demons with his newfound power, desperate to stop the downfall of all human civilization.

[Written by MAL Rewrite]

Devilman

デビルマン

Oku, Hiroya

Lonely high school student Kei Kurono isolates himself out of a growing cynicism toward his fellow man and the cruelty they are capable of enacting. One day, while waiting to take the subway to school, Kei's classmate Masaru Katou leaps onto the tracks in an effort to save a drunk man. Driven by an uncharacteristic desire to rescue someone else, Kei follows Katou down into danger. While successful in saving him, the two boys are killed by the train.

Kei wakes up beside Katou in an apartment full of strangers and furnished by a giant black orb with a glass-like outer surface. After finding out that everyone in the room has recently died, words appear on the black ball tasking them with killing a strange creature. The ball equips Kei and the others with power suits and mysterious guns before sending them off to collect this bizarre bounty.

Although Kei discovers the mission to be far more deadly than originally suspected, he manages to survive. He is teleported back to the apartment where he and the other survivors are rewarded point values according to their actions in battle by the black sphere, which a fellow survivor says is called "Gantz." Despite his death earlier that day, Kei is granted the ability to return to his daily life with one condition: he can be uprooted from his day at any time and summoned back to the apartment, where Gantz will task him and other recently deceased with the assassination of another target. 

While Katou dreads the inevitable return to Gantz, Kei finds himself living for the sole purpose of carrying out these missions. Thriving in the heat of battle and learning to care about himself and his comrades, Kei faces escalating monstrous threats that begin to bleed out into his normal life outside of Gantz.

[Written by MAL Rewrite]

Gantz

GANTZ

Nanatsuki, Kyoichi

Night Owl

The world has become a desolate, lawless land where bandits roam free, innocent people suffer and demons lurk around every corner. Sona Yuki is traveling with his family when they are attacked by bandits, his entire family is murdered and he is left with a snake mark on his hand. As he is about to die, a woman comes up to him and gives him an option: continue to live in this harsh environment or die peacefully now. Yuki chooses life and Garami, the woman, gives him a second chance at life in exchange for his servitude. Garami is a weapons merchant and a gun for hire that travels from town to town for clients. Yuki sees how brutal and unforgiving this world can truly be.

(Source: MangaHelpers)

Kiba no Tabishounin: The Arms Peddler

牙の旅商人 ～The Arms Peddler～

Mikage, Eiji

Tetsuo

Kazuki Hoshino values his everyday life above all else. He spends the days carefree with his friends at school, until the uneventful bliss suddenly comes to a halt with the transfer of the aloof beauty Aya Otonashi into his class and her cold, dramatic statement to him immediately upon arrival:

"I'm here to break you. This is the 13,118th time I've transferred. After so many occasions, I have to say that this is all starting to grate on me, which is why this time I'm spicing things up with a proper declaration of war."

And with those puzzling words, the ordinary days that Kazuki loved so dearly become a cycle of turmoil and fear—Aya's sudden appearance signals the unraveling of unseen mysteries surrounding Kazuki's seemingly normal friends, including the discovery of mysterious devices known as "boxes."

[Written by MAL Rewrite]

Utsuro no Hako to Zero no Maria

The Empty Box and Zeroth Maria

空ろの箱と零のマリア

Miura, Kentarou

Studio Gaga

Guts, a former mercenary now known as the Black Swordsman, is out for revenge. After a tumultuous childhood, he finally finds someone he respects and believes he can trust, only to have everything fall apart when this person takes away everything important to Guts for the purpose of fulfilling his own desires. Now marked for death, Guts becomes condemned to a fate in which he is relentlessly pursued by demonic beings.

Setting out on a dreadful quest riddled with misfortune, Guts, armed with a massive sword and monstrous strength, will let nothing stop him, not even death itself, until he is finally able to take the head of the one who stripped him—and his loved one—of their humanity.

[Written by MAL Rewrite]

Included one-shot:
Volume 14: Berserk: The Prototype

Berserk

ベルセルク

Mizukami, Satoshi

Fuuta Okeya, a 14-year-old student, can see ghosts and wears a bandage on his left cheek to hide his striking birthmark. One day, a girl with a scar on her forehead named Kouko Ishigami, accompanied by a ghost of a tall and friendly man, transfers into his class.

Fuuta quickly takes a liking to Kouko, wondering if it might be love at first sight. After waking up crying from a strange dream involving her, he feels a nostalgic connection to Kouko and becomes determined to befriend her. However, a chain of events forces Fuuta to reveal his birthmark to Kouko, to which she declares him to be the enemy of her life. A furious Kouko explains that the two are bound by reincarnation, and that Fuuta's birthmark is a curse she engraved on him in one of their past lives to recognize and eventually defeat him.
 
Kouko brings out a circular object made of flames known as the "spirit circle" and attacks Fuuta, pushing him off a flight of stairs. As he falls, Fuuta is thrown back into the insight of one of his previous lives. Spirit Circle chronicles Fuuta's journey back and forth his several past lives as he gradually unravels the mysteries behind his apparent bad blood with Kouko.

[Written by MAL Rewrite]

Spirit Circle

スピリットサークル

Samura, Hiroaki

Manji is an infamous swordsman in feudal Japan who is known as the "Hundred Man Killer," as he has killed one hundred innocent men. However, there is something far more frightening than his ominous reputation: the fact that he is immortal. This is the handiwork of eight-hundred-year-old nun Yaobikuni, who placed bloodworms capable of healing almost any wound in Manji's body. 

To atone for his crimes, Manji resolves to kill one thousand evil men. Yaobikuni agrees to this proposal, saying that if he succeeds, she will undo his curse of immortality. Soon after this promise, Manji meets Rin Asano, a 16-year-old girl who requests Manji's assistance in killing those who slaughtered her parents.

Initially reluctant, Manji refuses Rin's desperate plea. However, owing to her evident lack of strength, Manji changes his mind and agrees to protect Rin for four years. With this partnership set in stone, the two embark on a perilous journey of bloodshed, vengeance, and redemption, each to fulfill their own life's cause.

[Written by MAL Rewrite]

Mugen no Juunin

Blade of the Immortal

無限の住人

inee

One fateful day, Koharu is saved from an untimely end and reborn as a Cupid. Her mission: bring love to humans and earn a second chance at life. But modern problems call for modern solutions, and the Cupids of today have traded in their outdated bows and arrows for high-velocity firearms! Koharu's happy to dutifully help others find love, but her eccentric mentors don't play by the book and will happily turn an argument over a love triangle into a battlefield of tactical matchmaking action!!

(Source: Yen Press)

Love Bullet

ラブ・バレット

Yamamoto, Hideo

Susumu Nakoshi is a middle-aged man who spends his days between a lavish first-class hotel and a park full of homeless people. One day, an eccentric young man approaches Nakoshi in search of subjects willing to partake in trepanation—the procedure of drilling a hole in the skull. 

This mysterious person claims that Nakoshi is the perfect man for the experiment. Initially rejecting the offer, he doubles back on his decision after his car gets towed off. Nakoshi agrees to let Manabu Ito, a 22-year-old medical student, drill a hole in his skull in exchange for 700,000 yen. The procedure bears no results at first, with Nakoshi showing no abnormalities. This normalcy comes to an abrupt end, however, when Nakoshi begins seeing the homunculus in every person. With his perception distorted, how will Nakoshi face these homunculi?

[Written by MAL Rewrite]

Homunculus

ホムンクルス

Nihei, Tsutomu

In an enormous steel labyrinth riddled with horrifying creatures, humanity is forced to isolate itself in small enclaves while living in constant fear of its annihilation. In this dystopia, only a strange young man known as Killy is brave enough to traverse its unforgiving territories. 

Possessing superhuman strength and a rare Graviton Beam Emitter, Killy fights off bloodthirsty beasts and other fiendish forces in his desperate search for a human with the Net Terminal Gene—genetic information that holds the potential to restore the corrupt world. 

The dark world of Blame! follows Killy as he meets new people, sheds more blood, and draws closer to finding the Net Terminal Gene. Through these exploits, the true nature of the world is slowly pieced together.

[Written by MAL Rewrite]

Blame!

BLAME!

Yoon, In-Wan

Yang, Kyung-il

In Jushin, there once lived secret government agents called the amen osa (or angyō onshi in the Japanese version), who traveled the countryside in disguise. They were charged by the king with finding and punishing corrupt government officials, and bringing justice to the country's citizens.

(Source: Wikipedia)

Shin Angyo Onshi

Blade of the Phantom Master

新暗行御史

Hirano, Kouta

For centuries, many secret organizations have taken part in exterminating various types of dangerous monsters. One of them is the England-based Hellsing, run by its cunning leader, Sir Integra Fairbrook Wingates Hellsing. Her greatest hunter, and trump card, is Alucard, an unbeatable vampire genetically modified by her father. Despite him being one of "them," he swore to be her protector and servant.

A new crisis begins and with the help of Seras Victoria, his recently turned vampire partner, Alucard has to uncover the truth behind the mysterious vampire attacks. Not every human is bound to be his ally in this battle, and he will not hesitate to kill anyone who stands in his way.

[Written by MAL Rewrite]

12 Manga Like Devilman Tai Yami no Teiou