I'm a Pastor, what the hell is an Acute Gastroenteritis Outbreak Spell?! - Chapter 455 - 350 Skill Failure? Alzheimer’s Forgetfulness Spell!_3

Utsuro no Hako to Zero no Maria, or The Empty Box and The Zeroth Maria, tells the sinister story of Kazuki Hoshino, who is almost madly attached to his everyday life, and his antagonist Aya Otonashi, who suddenly transfers into his class—for the 13,118th time. She majestically announces to “break” him, without paying heed to anyone else around them.

They call him Ghost.A name whispered in fear across warzones, black markets, and underworld circles.To the world, he's a phantom—a faceless mercenary who leaves no trace but bodies in his wake.To his enemies, he’s a death sentence.To his brothers-in-arms in Graveyard, he’s family.But to himself... he's a haunted man searching for a past stolen in gunfire and smoke.After a flawless mission deep in the Eastern Province, Ghost returns to the hidden forest base he's called home for sixteen years. Yet the victory is short-lived. His foster father, the commander delivers an unexpected order:“That was your last mission.”Now, Ghost—real name Miles Sterling—must step out of the shadows of war and into a world he’s never known. Guided only by a scarred letter, a fading memory, and the voice of a woman he hasn’t seen since the day everything was taken from him.But war forged more than his body and name.Behind the mask, behind the scars, Miles has another secret.One he’s kept hidden even from his brothers in arms.He’s not just a weapon.He’s a ghost with a fortune—a hidden empire he built in silence, across borders and black markets, forged in strategy and blood.A man of many names, and many shadows.Beneath the bullets, tattoos, and silence lies a truth buried in ashes.And Ghost is about to dig it up—one letter, one enemy, one memory at a time.

This is a world where humans, demons and mysterious beasts coexist.

Humans cultivate mysterious qi. Demons cultivate corporeal bodies. Mysterious beasts cultivate soul perception.

A legend says that in the middle of an endless rainforest, there are extremely powerful existences; they are called demon kings.

Some demon kings have a tyrannical corporeal body, some are experts in illusions.
Some demon kings are proficient in magic, some can even move mountains.
Some demon kings are able to sense things thousands of miles away.

These demon kings rarely appear in the human world. Even if they emerge in the human world, they would reincarnate in human form; assimilating with mankind while seeking to breakthrough realms…

- Description from Novelupdates