At the beginning of the Edo period (1603-1868), when people enjoyed a time of peace, Lord Tokugawa Tadanaga decides to hold a fighting tournament. In the past, matches were fought with wooden swords, but this time real swords will be used. The one-armed Fujiki Gennosuke and the blind Irako Seigen will fight each other in this tournament, even though both of them are disciples of Iwamoto Kogan — known as Japan's greatest swordsman. So begins the story of intertwining fates, conflict, and strange destinies.

One of Go Nagai's first works, this violent period piece takes place in the 1500s and stars a talented, low-ranking ninja named Shishimaru. In it, Shishimaru fights against Ginnai Doma (an immortal samurai who, despite being butchered multiple times, doesn't die) because Ginnai murdered his comrades.

Despite being set in historical times, it has time travel, aliens and the alternate universe war.

From MangaHelpers:
The world is in a war against an alien race called "Mimics," who have taken over most of the world with a mission to eliminate the human race. Keiji Kiriya is a new recruit in the United Defense Force, which is battling against these "Mimics." On his first day of deployment, Keiji and his unit encounter "Mimics" and are all killed... Or was it all a dream? For some inexplicable reason, after every time he dies, he is resurrected and returned back to the day before the battle. Why does this happen to Keiji and how can he escape from this never ending cycle?

Note: Nominated for the Eisner award for the "Best U.S. Edition of International Material - Asia" in 2015.

Michi is a girl given extraordinary power by her fairy godmother Yaaba...the power to transform into the beautiful and heroic Cinderella Knight. With these powers, she seeks to protect the man she loves from afar, the handsome Prince Emilio of Ballade, from the evil Spider Corps of the organization "MURDER"

From Wikipedia:

An innocent young man, Ikuroo, has a parasite known as Baoh implanted in his brain by an evil organization, Doress. The parasite makes him nearly immortal and gives him the ability to transform into a really powerful beastie when he's in trouble.

Doress intends to use him in some sort of ploy for world domination. But while they're moving him around, a young psychic girl, Sumire (who's also being held by the organization), sets him free, and the two escape together. Of course, Dr. Kasuminome is the mad scientist behind the whole thing, and he isn't about to let his test subject get away... and he has everything from superpowered lackeys to a small army at his disposal.

A collection of short stories:

1. Oral Cavity Infectious Syndrome
On the surreal premise that women's mouths take the often weird shape of their partner's penis, Yoriko starts an investigation to discover with whom her boyfriend is cheating.

2. Local Tourist Information
A guide to an extraterritorial region of Japan.

3. Back Streets in Front of the Station
A girl goes crazy about reverse sides of different things, including streets, cars, and animals.

4. Genesis
Kago Shintarou's rendition of the Book of Genesis.

5. Superglue
What happens when you step on something so disgusting that you never want to uncover it?

6. Akutagawa in Front of the Station
A surreal homage to the writings of Ryunosuke Akutagawa.

7. When All's Said and Done - also included in Hell Season
A gruesome tale of hardened faeces, and a limbless girl.

8. Multiplication
Comic panels are multiplying and create opposing clans.

9. Abstraction
A two dimensional comic about young lovers turns 3D causing the characters' bodies to deform.

10. Blow-Up
What happens when every comic page features exponentionally more panels than the previous one?

11. No Need for Caution
The action of the comic happens outside of the panels--literally--in the white space.

12. The Memories of Others
Everyone's memories become visible via floating comic book panels.

13. Lord of the Ring
An incompetent sumo wrestler uses the powers of a forbidden pair of pants to overcome and shame his competition, until one day someone rises to attempt to crush him and take the pants for himself.

14. Spinning Thoughts
Wearing urinary calculi is the latest fashion trend.

Abara is set in a dystopian world, filled with large structures. The story revolves around creatures known as Gaunas, those who can shape bone like armor and weaponry around themselves by transforming. The transformation begins around the spine and then shapes layered armor.

The story focuses on one such Gauna known as Kudou Denji, though he uses Itou Denji as a fake name early on.

Abara means "ribs" in Japanese.

Volume 2 contains Digimortal
A mercenary in cyber-armor battles a repressive cyborg regime.

A sort of horror-mystery, Anamorphosis revolves around a group of people invited to a contest wherein they have to stay in a supposedly haunted set for 48 hours after an evil murderous spirit is summoned to produce a recreation of the murder scene.

Over half of the book features this story and the rest is a collection of bizarre shorts designed to make you go
( ﾟдﾟ)！？

Like the earlier Battle Royales, a class of middle school students are picked to compete in fights to the death on an island until there is only one left.
The manga follows the point of view of Girl #10 Makoto Hashimoto, an unlucky girl who fears that her class will be chosen to participate in "the program," a mysterious event that forces students to kill each other. Makoto attends Shikanotoride Junior High School. After the encouragement of her best friend Itou Yamamoto and her mother she decides to face the chances. Her fears are supposedly put to rest when word spreads that all 50 Programs had already been executed in the year making them 100% unlikely to participate....

Take yourself back to the 1880s where the KKK is thriving and the African American community lives in fear. The African Americans don't fear the KKK simply because they beat, rape, and kill them. No. They fear the KKK because the KKK eats them. They are the aptly named man-eaters, a kind of mix between werewolves and vampires. They consume human flesh, can shapeshift into various forms, and are practically immortal. Only one man, an ex-heavyweight boxer named Victor Freeman, dares to stand up to them. Equipped with a small arsenal and a set of modified brass knuckles, can our hero defend his people and avenge his past?

In a world where monsters called Yoma prey on humans and live among them in disguise, humanity's only hope is a new breed of warrior known as Claymores. Half human, half monster, these silver-eyed slayers possess supernatural strength, but are condemned to fight their savage impulses or lose their humanity completely.

The people of Earth live in a society where vampires aren’t just real but dangerous. Although humanity has been able to keep them under control and even take the night away as the vampire’s natural habitat, some of them have adapted. Hesperides, a relatively new breed of vampires, have adapted over hundreds of years in order to be able to go outside during dusk when the sunlight is at its weakest and feast on humans. Aburaya Shiro, a high school kid, lives in a town where there has not been a vampire attack in years, but adults keep warning them of going outside at dusk. Shiro and his classmates take this warning lightly and head out at dusk only to find out one of their classmates who they thought they knew well turnz out to be a Hesperides. With all his classmates violently murdered, the only way Shiro was able to survive was with the help of a different classmate, Ichijoji Eruka, who doesn’t seem to be human herself.

Fudou Jun is a highschool teacher and takes a trip with a group of students. While there, a group of martial artists staying nearby take a strange interest in the girls.
These men are actually demons and after changing into their true form break into the cabin to rape the girls. One gets Jun and violates her.
She feels her soul being torn apart and transforms into Devilman Lady. With newfound powers and strength she kills all the demons and protects the girls from any further harm.
What are these demons and why did she turn into a hybrid of one? What does this mean for her and for the rest of humanity?

The story involves human mutations called "Diclonius", who grow horns on their heads and possess telekinetic powers, in the form of invisible "arms" called vectors.
The tendency for violence among Diclonii varies among characters. Certain scientists contain them in a Facility in cells, where they are subject to inhumane experiments to test their abilities or where they await execution for being too dangerous.
An infectious virus is also associated with the mutation. This virus is spread through non-lethal contact with the vectors of a diclonius.
The main non-mutant character in the story is Kouta, who ends up becoming increasingly involved with these dicloniuses, as they seek refuge from the scientists.
The main diclonius character is Lucy/Nyuu, a killer whose alter ego is a hapless and very cute child whose vocabulary and intelligence are quite limited.

At the end of the 21st century, humans have made great advancements in technology and were able to create a giant energy source to power that technology. However, this new source of energy overloaded and turned into a more devastating force than nuclear weapons. The catastrophe wiped out the majority of human civilization and those who survived lived in terror of the anarchy that took over. Hagakure Kakugo comes from a secret family that has protected people for generations from powerful organizations and evil from taking over. They are only awoken in time of need and it has been decades since Kakugo was conscious. His body had been heavily modified by fusing it with metals to enhance both his offense and defense. He uses an armor called the Exoskull that attaches to him to greatly boost his already superhuman power. Thus begins a story about a young man and his armor’s journey through hell.

199X, nuclear war has ravaged the planet. From the ashes, gangs have risen to take all the power from world governments. Justice has ceased to exist in this now lawless world. From the sands of a desert, a man appears. His name is Kenshiro, and he is the sucessor to the most powerful martial art in the world, Hokuto Shinken. This art attacks the foes insides, and makes them explode internally and die in often brutal ways. Kenshiro's goal is to kill the man who kidnapped his fiance, Yuria. A man that he once called a friend, but who betrayed him and left him for dead. Along the way, he makes friends and enemies alike, while protecting those who cannot protect themselves.

Fear runs rampant throughout Tokyo with the revelation that demons in fact exist amongst us. Paranoia and the darker side of humanity boils onto the streets as people turn on one another, suspecting that anyone could in fact be a demon hiding in human clothing. Amidst the growing tensions, tragedy strikes Akira causing his mind to snap, retreating into his subconscious, allowing his Devilish alter-ego Amon to break free from Akira's cage of flesh and wreak havoc on both human and demons alike.

Ryo and Akira travel through time in order to eradicate demons that could have changed history. Various periods are visited: from pre-WWII to ancient Greece, middle ages in France meeting Joan of Arc, far-west America, renaissance.

When demons begin taking over the bodies of humans, only the strongest survive. When a practicing young witch named Miki Makimura asks her friend Akira Fudou for help with a ritual, the spell is interrupted and Akira is left on the brink of death. His body is overtaken by a powerful being named Amon. Now torn between his humanity and the demon within him, Akira uses his abilities to fight in the war between demons and humans for the future of the world itself!