The Insider System - Chapter 27: Light Temple

An unexpected discovery in Machu Picchu has transported a young professional thief from Earth to a world filled with mystical powers and evil plots. With his beloved teacher and best friend killed during the calamity, his only goal is to become stronger, so that he can take revenge for them.This is a novel filled with politics, the struggle for power, evil beauties, and of course, Divine Immortals.

- Description from Novelupdates

High school student Mikoshiba Ryouma was summoned to a different world in the middle of a war. Sensing the malice from the one who summoned him (a summoner of the O’ltormea empire), he uses his martial arts to run away, killing important people of the empire during his escape. After the escape, he rescues two twin sisters from the hands of thieves. The sisters who can use magic, swear to serve him as subordinates. Thus, Ryouma begins his journey on the path of the supreme ruler.

The sky was painted gray forever. The light of the sun was restrained. The darkness of the night was deeper than ever. At such a time, he belonged to a class people didn’t even recognize as ’human’. He was at the bottom of the social stratum, a slave. And when his only family was taken away from him... he no longer had a purpose in life. Yet, he clung to life because of his promise. And he set an impossible goal for himself, just so he’d have an excuse to live. When he finally reached a place he never expected to be, in pursuit of a purpose he expected to fail and die miserably trying to fulfill... he awoke to a night that would change his entire life. He was an insignificant fly, a mere speck in the destruction of the Empire. But he... survived. And, despite being a slave, he gained the blessing of a king. Or rather, the curse...

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.