MTL - Boneless Incense - Chapter 4

Yo, Hi! I’m Frank, I made a deal with a demon to pay me some money for receiving a guest for a few days every week.
I had no idea about what I have done.
On May 1st, Conan ‘the God of Death’ came to my house. I was forced to let him in and we get involved in a criminal case.
On May 8th, Bruce Wayne ‘Batman’ came to me. I was forced to follow him to fight crime.
On May 16th, Hannibal Lecter, The Silence of the Lambs, came to my home. I can only say that I really can’t stand my guests.

- Description from Novelupdates

In a world where magic intertwines with reality, a dying human girl named Elara awakens to find herself in a foreign land. The air smells of ancient forests, and the sky is painted with hues she’s never seen before. Before her stands the enigmatic Demon Queen, Seraphina, her eyes as cold as the ice that encases her throne.Seraphina proposes a desperate bargain: a contractual marriage between them. In exchange for Elara’s hand, Seraphina promises to save the crumbling human kingdom from impending doom. Elara, with nothing left to lose, accepts, thrust into a web of intrigue, danger, and forbidden emotions.As they embark on their perilous adventure, Elara discovers that Seraphina’s icy demeanor hides a tragic past. The Demon Queen’s power is unmatched, her wrath swift and merciless. Yet, beneath the frost, Elara glimpses vulnerability—a longing for connection that defies her ruthless reputation.

Within the virtual world of “Avalon Online”, Finn, or otherwise known as “Echo” within the game, was one of its greatest players. After logging off from a long session, however, he notices something awry outside of his apartment.The streets were flooded with chaos, screams echo through the night, and hell is loot loose. Monsters from Avalon Online are running through the streets, wrecking havoc. In the midst of this hellish awakening, Finn is greeted with the one gift bestowed to humanity in this dark hour:[...Assessing life experience…][Assessment Complete][Name: Finn Thorne][Age: 20][Designated Class: Assassin][Starting Level: 5][A [Legacy System] has been bestowed to you for your accomplishments within Avalon.][Assimilation System Awakened.]In this twisted turn, as the world as it was once known is gone with the arrival of magic and monsters, the remnants of humanity must level up if they wish to survive.Finn is left in this dark, hopeless apocalypse, using his own experience from Avalon Online to best survive what seems to be an impossible task.

I want an S-Rank skill too! I want it so badly, I could die for it!