Akuma-kun (1989)

It has been 800 years since the incredibly fast and powerful gods of battle known as the Idaten had sealed away the demons after an intense battle. Now, that battle is just considered a myth or a fairytale. While the current generation of Idaten who have never even had to fight are enjoying their peaceful lives, someone awakened the demons once again! Armed forces, ingenuity, politics, and intrigue. If you've got it, use everything you can! This three-way battle royale with no rules and no limits is about to begin!!

In his past life, he was known as Demon Lord Varvatos, an all-powerful magic user and ruler. But he was lonely after the loss of his friends and loved ones during his rise to power, so in his dying moments, Varvatos cast a reincarnation spell so that he'd get a second chance at just being a normal guy. At first it looks like that's going to work – he's reborn thousands of years later as villager Ard. Unfortunately for him, his memories are still intact and he's not aware just how much has been lost over the time he spent not existing, and it looks like that's going to cost him his normal life.

A century has passed since King Kyle of the Orvelia kingdom destroyed the fierce demon lord Angmund, restoring peace to the lands. Now in a time of peace, the apprentice knight Kasel enjoys his life without worry. His fate begins to change, however, with news of demon appearances infesting the neighborhood. Guided by a wise man, Kasel finds friends he can rely on and sets off on his mission to seek a holy sword, capable of slaying his newfound enemies.

Destructive monsters from the Mato dimension threaten the earth, while women gifted with powers from Peaches try to stop them. But to save the world, Yuuki must be willing to become Chief Kyoka's servant both on the battlefield and at home.

A door to another world stretches out before a boy who's been brutally bullied all his life. This alternate reality grants him access to all sorts of things, like cheat skills and a portal that lets him travel between his old and new worlds! Can this class loser turn his life around back home...?

Anos Voldigord was a tyrannical Demon King that eradicated humans, spirits, and even the gods, but became bored of eternal warfare and reincarnated with dreams of a peaceful world. However, what awaited him in reincarnation after 2000 years were descendants who became too weak after being accustomed to peace, and all sorts of magic that deteriorated to the extreme. Anos enters Demon King Academy that gathers and educates those who are viewed as the reincarnation of the Demon King, but the academy could not see through his true powers and ends up branding him as a misfit.

Waking up in a strange new place with no memory of his past life, Kelvin learns that he's bartered away those very memories in exchange for powerful new abilities during his recent transmigration. Heading out into a whole new world as a Summoner — with his first Follower being the very goddess who brought him over! — Kelvin begins his new life as an adventurer, and it isn't long before he discovers his hidden disposition as a battle junkie. From the Black Knight of the Ancient Castle of Evil Spirits to the demon within the Hidden Cave of the Sage, he revels in the fight against one formidable foe after another. Join this OP adventurer in an exhilarating and epic saga as he and his allies carve their way into the annals of history!

There was once a man who was summoned to another world, and saved it. Of course, he became too popular there, and turned into an isekai-normie. However, that man fell into a "trap" and was forcibly returned to his original world. Moreover, he had to start over as a baby! This is the story of the way-too-fantastic ex-hero who lived as a gloomy high-schooler, as he gets summoned once again to that same other world in a very unexpected development!

Turns out, evil takes initiative! With world domination close at hand, the Kisaragi Corporation turns its sights on interstellar conquest, and who better to take over a magical world than two randomly assigned minions—Combatant Agent Six and his android partner Alice? But Six’s path up the evil corporate ladder won’t be easy—a Demon Lord’s army is hatching its own nefarious plan!

In a city of the dead, long since ruined and far from human civilization, lives a single human child. His name is Will, and he's being raised by three undead: the hearty skeletal warrior, Blood; the graceful mummified priestess, Mary; and the crotchety spectral sorcerer, Gus. The three pour love into the boy, and teach him all they know. But one day, Will starts to wonder: "Who am I?" Will must unravel the mysteries of this faraway dead man's land, and unearth the secret pasts of the undead. He must learn the love and mercy of the good gods, and the bigotry and madness of the bad. And when he knows it all, the boy will take his first step on the path to becoming a Paladin.