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

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

Iwaaki, Hitoshi

"Parasites" are tennis ball sized creatures, whose numbers and origins are unknown. They invade and take over the human mind in order to survive. Shinichi Izumi is a 16-year-old high school student who lives with his parents in a quiet neighborhood. One night, a Parasite invades Shinichi's body in an attempt to take control of it. However, it fails to complete the takeover process and ultimately ends up inhabiting only his right arm. 

Thus, both Shinichi and the Parasite—who calls himself Migi—retain their individual minds. Now in a peculiar "human and alien" relationship, Migi proposes that they cooperate to survive. Shinichi has no choice but to agree, and he must now cling to his morality as he and Migi face off against other bloodthirsty Parasites.

[Written by MAL Rewrite]

Kiseijuu

Parasyte

寄生獣

Matsumoto, Leiji

In the future, humanity has achieved a vast starfaring civilization, but is slowly and steadily succumbing to ennui or despair, often due to defeat and subjugation by a foreign invader. Rising against the general apathy, Herlock denies defeat and leads an outlaw crew aboard his starship Arcadia to undertake daring raids against Earth's oppressors. Their primary oppressors are the Mazone, a race of organic plant-based alien women who explored Earth in the mythic past and are now back to reclaim it.

(Source: Wikipedia)

Uchuu Kaizoku Captain Herlock

Captain Harlock

宇宙海賊キャプテンハーロック

Otomo, Katsuhiro

Nagayasu, Takumi

Orbiting serenely above a long-ago poisoned earth, the last bastion of human civilization is the space colonies. After a terrorist attack, the colonists are forced into exile on the blighted planet below. In the confusion, a young mother is separated from her family and is flung into a bleak, uncertain future... But Sarah will not rest until she finds her children.

(Source: ANN)

Sarah: The Legend of Mother Sarah

The Legend of Mother Sarah

沙流羅 -The Legend of Mother Sarah-

Ogino, Makoto

A young mystic without a past, Kujaku was born under a dark omen possessed of incredible supernatural powers. Raised by priests, he has learned to use these powers for good. But the evil Siegfried von Mittgard seeks to steal his birthright, and rule the world as the Regent of Darkness. He has dispatched bloodthirsty minions to destroy Kujaku before he can awaken to his destiny. Now, Kujaku must unravel the riddle of his past, before the power within consumes him!

(Source: AniDB)

Kujakuou

Peacock King

孔雀王

When a miner on the industrial planet Chakra is attacked by an unknown animal yet somehow survives, Trouble Consultants Kei and Yuri are called in to investigate. How did the miner survive his wounds, and what are the ulterior motives of the company-town's superiors: the enigmatic religious leader, the town mayor, and the owner of the mining facilities? The answers will shock the two women and embroil them in yet another highly dangerous - and highly destructive - adventure!

Features the original cover and nine interior illustrations by Yoshikazu Yasuhiko, character designer for such anime as Mobile Suit Gundam and The Venus Wars, for which he was the writer, character designer, and director.

Written by Haruka Takachiho.

(Source: RightStuf.com)

Dirty Pair Strikes Again

ダーティペアの大逆転

Miyama, Noboru

"Put an end to this cursed world! That is your fate!" An alchemist by the name of Godot whose father was charged with theft must seek revenge for his father and his own freedom as he participates in the fighting festival known as Valhalla.

(Source: Kodansha, translated)

Godot

ゴドー

Hoshino, Yukinobu

Bem, the bounty hunter engaged in a hunt "bloody", a mythical creature, on a planet at the dawn of evolution.

Bem Hunter Sword

ベムハンター・ソード

Included one-shot:
Volume 2: Frankenstein II

V2 Panzer

V2パンツァー

Tanaka, Yoshiki

Katou, Naoyuki

Kamoshita, Yukihisa

In the far future, two young military leaders rise above their peers. The invincible genius Reinhard von Lohengramm is matched only by the unbeatable magician Yang Wen-li; though the two share a profound respect for each other, they meet on the battlefield not as comrades but as bitter adversaries. Commanding thousands of warships and millions of soldiers, they lead giant space fleets into battle on behalf of the two interstellar states that have wrested for control of the Milky Way for over a century and a half. 

The Galactic Empire, an absolute monarchy ruled by Kaiser Friedrich von Goldenbaum IV and an entrenched nobility, seeks to suppress the rebels daring to oppose the inviolable crown. The Free Planets Alliance, a representative democracy led by a corrupt High Council, degenerates as its elected leaders⁠ use war and conflict as a way to win popular support. Reinhard is a minor noble who became a High Admiral through his strategic brilliance and his sister's position as the favored concubine of the Kaiser, while Yang is an avid historian and reluctant commodore hailed as a hero despite only using his tactical prowess to navigate around his leaders' incompetence. On opposite sides of the galaxy, the two men have wildly different visions for the future: Reinhard dreams of uniting mankind under his iron fist, while Yang wants only to carve a path to lasting peace. As the war rages on, Reinhard and Yang each strive for their ideals and secure their place among the stars as the leaders of a new era of galactic heroes.

[Written by MAL Rewrite]

Ginga Eiyuu Densetsu

Legend of the Galactic Heroes

銀河英雄伝説

Takaya, Yoshiki

Sho and his friend, Tetsuro, stumble upon a strange orb-like mechanism, the Guyver Unit, in the woods. It physically bonds with Sho and turns him into the alien soldier, Guyver. His mission is to protect the Guyver Unit from the Japanese corporation known as Chronos. They are after it and two other units just like it. To retrieve the object, they send out vicious monsters known as Zoanoids. So no one is safe in Sho's life; not even himself.

12 Manga Like Kamen Rider Spirits