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

Shimizu, Aki

Okuse, Saki

Three centuries ago, a vampire by the name of Migiri was running a reign of terror across Japan when a hero named Naonosuke Kobayashi cut off his head and sent him to eternal rest... until now.

(Source: Tokyopop)

Yato no Kamitsukai

Blood Sucker: Legend of Zipangu

夜刀の神つかい

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

Hokazono, Masaya

Matoba is a reporter in Japan. He went to Arizona to search for a missing poet named Saeko. While he was at the desert of Arizona, Matoba met a strange man called Godo. This encounter resulted him to go through countless supernatural events that he tried to explain with scientific resasons but failed. Later, Matoba discovered he was on the way to became a "Wiseman" and would learn Godo and Saeko's objective that would change the whole world.

Wiseman

ワイズマン

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

Hosono, Fujihiko

Two scientists are attempting to distribute the cure for a demon virus that is affecting people all over Japan, however, things have become complicated. One of them has become infected. So begins his battle with himself, as he attempts to not only control his emerging demon side, but also to save the lives of others by wielding its great strength.

Bio Hunter

バイオ・ハンター

Adachi, Mitsuru

The story is set in a place very similar in appearance to Earth in the Edo period. However, Adachi (the mangaka) regularly reminds the reader all throughout the series that the setting is another planet in the distant future which just happens to look like Earth.

After the death of his mother, Shichimi sets out to join his step-brothers and -sister who live together in Karakuri Tenement, a place provided by the father they have never met. He finds out that each of them had different mothers (all of whom have died), but were fathered by the same man. Not long after Shichimi's arrival, the siblings decide to journey to visit the graves of each of their mothers. On this journey, they encounter many dangers.

(Source: Wikipedia)

Nijiiro Tougarashi

虹色とうがらし

Manabe, Jouji

It`s face-to-face confrontation when Kahm stares down her father and refuses to end her relationship with Tetsuya. In retaliation, her father sends a punitive fleet to Earth -- with orders not only to crush the rebellion but to annihilate the entire solar system!

(Source: Amazon)

Outlanders

アウトランダーズ

Tezuka, Osamu

After the cruel lord Daigo Kagemitsu sells his newborn son's body parts to 48 demons in exchange for power, he casts what remains down a river and quickly forgets about his son, soon establishing a mighty kingdom. Little does Daigo know that his child survives, possessing advanced spiritual senses that allow him to navigate the world without eyes, ears, limbs, or even a voice.

A brilliant doctor rescues the son and raises him as his own, naming him Hyakkimaru and fitting him with advanced prosthetics that make it possible for him to move and fight. However, tragedy strikes when Hyakkimaru turns out to be a beacon that brings demons into the doctor's home, and the doctor eventually has to send Hyakkimaru out into the world.

Amid his travels, Hyakkimaru learns that slaying demons allow him to recover his missing parts and seeks to kill enough to make himself whole. He soon encounters Dororo—a boy claiming to be the world's greatest thief—who joins Hyakkimaru against his will in hopes of one day obtaining his sword. Together, the duo travels through a countryside infested with both demons and brutal men, who might prove to be worse.

[Written by MAL Rewrite]

Dororo

どろろ

Ishikawa, Ken

The first Getter Robo series chronologically published 15 years before the rest of the manga. Getter Robo pioneered the idea of the combining and transforming robot.

Millions of years ago, the dinosaurs were driven deep underground due to the sudden arrival of "Getter Rays" on Earth. After evolving into sentient beings, they grew bitter and vengeful at the humans who replaced them on the surface and began plotting their attack on humanity.

Fighting against them is Getter Robo, a machine built by Professor Saotome which uses the mysterious Getter Rays as its power source. Piloting it are three strong-willed young men—the violent martial artist Nagare Ryoma, the psychopathic yet highly intelligent revolutionary Jin Hayato, and the hot-blooded judo master Tomoe Musashi. Each controls one of three specially designed combat jets which can be combined together in different forms to form three different kinds of giant robots: the flying, axe-wielding Getter-1, the quick, drill-wielding Getter-2, and the tough, tank-like Getter-3.

Manga Like Godzilla vs. Mechagodzilla: Kessenshi