After the Fake Young Lady Stole Everything from Me, I Became the World’s Sweetheart - Chapter 448 - Four-Hundred and Forty-Eight: Appointment 2

Once upon a time, an Alchemist Grandmaster from the World of Immortals accidentally took possession of a playboy, who hailed from a rich and powerful family, and became a student in the middle of his midterms.

By the means of a miraculous immortal technique, he blended in and mingled amongst the femme fatales’ group to dominate the city! The nature of this novel’s origin is shamelessness to the core; having no sense of shame is just a basic foundation, but if the most shameless isn’t set yet, then become it!

- Description from Novelupdates

The world was once at war with 10 alternate worlds. This was known as the Concept War and our world won 60 years ago. All of this was concealed so no normal people are aware of this fact in the current time.

After the death of his grandfather, the high-school student Sayama Mikoto is suddenly summoned by the giant corporation IAI. He learns this world is headed for destruction due to the acceleration of the Minus Concepts. To prevent this, negotiations must be undertaken with the survivors of the other parallel worlds so their 10 concepts can be released.

And so Sayama is caught up in the final battle to clean up after the Concept War which left behind so much enmity.

A god of a different world had abruptly appeared in my classroom and semi-forcibly summoned the entire class to his world.ーーーーexcept for me, Kamiya Yato.

This story is set during the end of the Sui Dynasty, a time where multiple powers struggled for supremacy and power.