MTL - The Upgrade System of All Realms Starts From Conquering Naruto - Chapter 2 Since you came to the door yourself, I won't be polite.

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.

Poisoned by his wife, betrayed by his best friend, and abandoned by his children—Matthew died broken and alone. But when he wakes up thirty years in the past, trapped in his eighteen-year-old body, everything changes.Now, the halls feel haunted, memories from a future that may never come keep popping into his head, and something strange is growing inside him—something he can’t explain. Sadly, this second chance isn’t a blessing. It comes with a price.But this time, he won’t be the victim. This time, he’s the one in control.

Read at least six chapters, then prepare to crave the rest.The main character will show up in Chapter Five, though I don't recommend skipping the first four chapters.-----The world was celebrating. The Demon King was dead, along with his Darkness Generals.Humans led the other races to war for subjugation. They killed all, and none were spared. However, thousands of years before this happened, a piece of history was altered by time itself. In fact, the Demon King didn't have four generals but only one, which he sealed and sent into eternal slumber. Just as he started to close his eyes, the chains locked away for eternity shattered into pieces.