The God of Underworld - Chapter 81 - 35:

Hace 24 años, el mundo colapsó. Un virus conocido como Eclipse transformó a la humanidad en criaturas mutantes, llevando a la sociedad al borde de la extinción. Las ciudades se convirtieron en ruinas, los asentamientos luchan por sobrevivir, y la verdad sobre el origen de la infección se ha perdido en el tiempo.En este mundo roto, Kai, un viajero solitario y mercenario de intercambio, sobrevive negociando Obsidianos, la única moneda de valor en la nueva era. Su vida cambia cuando cruza caminos con Lía, una misteriosa joven perseguida por mercenarios. Su única posesión es un antiguo colgante de Obsidiano, cuyo secreto podría cambiar el destino del mundo.Juntos, se ven envueltos en una conspiración que los lleva hasta el Laberinto Ancestral, un lugar prohibido que esconde la verdad sobre el Eclipse. Perseguidos por un ejército liderado por el despiadado Voss, enfrentándose a infectados más allá de la comprensión humana y descubriendo que su pasado está conectado al desastre, Kai y Lía deberán decidir si la verdad merece ser revelada… o si es mejor que permanezca enterrada.Cuando la última puerta del Laberinto se abre y los ecos del pasado despiertan, solo una pregunta queda en el aire:¿Es el Eclipse el fin de la humanidad… o su evolución?

This novel is also known as I Possessed a Demon Sovereign

Chen Luoyang felt that something was wrong with his transmigration. After transmigrating, he possessed the body of the highest expert in the world, the Master of the Demon Cult, addressed respectfully as the Demon Sovereign.

Generally, aren’t supreme experts the ones that leave behind a wisp of their soul behind and occupy a new body of some miserable low-level youngster then they go on a journey of revenge and make a comeback?!

Or perhaps it would be transmigrating into a miserable youngster’s body and obtaining a cheat slowly walking the road to becoming a God?

But why did his transmigration seem wrong?

Now my environment is full of big shots and I feel like I’m going to be exposed!

- Description from Novelupdates

When a terminally ill young man awakens in the world of his favorite childhood game, he realizes he isn’t the protagonist, the destined hero, or even a major side character. Instead, he has become an extra—a disowned noble barely clinging to relevance in a world where strength determines everything. Worse, his fate in the game was to die an early, meaningless death.Armed with only his knowledge of the game’s storyline and a common system that tracks his stats and skills, he is determined to survive. But mere survival isn’t enough. He remembers a hidden easter egg from a long-forgotten anime collaboration: the Mangekyō Sharingan—a power limited by game mechanics but unrestricted in reality.With Kamui as his trump card, he walks the fine line between fate and freedom, seizing power from the shadows while avoiding suspicion. As the protagonist and his allies battle against demons and unravel the game’s grand destiny, he secretly builds his own strength—manipulating events, mastering forgotten arts, and even forging ties with villainous factions.Will he remain a footnote in history, or will he carve his own legend in a world that was never meant to be his?

It’s the vacation of a lifetime, a trip to a remote island filled with geniuses and murder.