MTL - Full Time Mage Lord - Chapter 2 Awakening (Book Request List)

After breaking up with his girlfriend, he accidentally acquired a genius system and rose from there against the heavens, becoming invincible..

- Description from Novelupdates

An ordinary youth living in the year 2050 in the Western calendar accidentally came to a fantasy world created by the collision of magical elements and supernatural technology at the other end of the dimension…

- Description from novelbuddy

This legend tells the tale of the protagonist, Kuroki summoned to protect the demon king from the hero.

Kuroki, unbeknownst to him, suddenly came to another world. He was summoned by the demon king, Modes. The territory which the demon king overrules was in the midst of being destroyed because of the hero. He had no choice but to bow before Kuroki.

“Please save us, Savior Dono!”

Kuroki nodded, deciding to save the demon king due to an unexpected turn of event.

In the vast and boundless continent Cangtu, there were ancient sects governing the Ten Old Domains, unworldly immortal clans beyond the Blue Sky, and primordial demon gods dominating the dark abyss that together created a great number of brilliant stories over the long course of the history.