The Empress's Gigolo - Chapter 901 - Video Clips of the Students’ Black History

A calculating merchant of noble birth lives a comfortable life managing his guild's business at the Imperial Academy—until lightning strikes him, leaving him with prophetic visions of a disastrous future. In these visions, he's expelled from his family, branded a traitor who aids demons, and worst of all, becomes a penniless beggar. When the supposed “protagonist” of these prophecies enrolls at the academy, he realizes his countdown to ruin has begun. Now he must use his foresight to rewrite a story where he's cast as a third-rate villain, all while navigating ancient dungeons, demonic threats, and the troublesome “hero” who might be the key to changing his fate.#MoneyIsEverything

A teenager named Evan Mason was reincarnated into the magical world of Harry Potter and goes to school at Hogwarts!
With only his knowledge of the future and great talent for magic, he takes the path towards the top of the magic world, only to realize that ever step he took, changed everything!

- Description from Novelupdates

Another entry in what you can call the Proto Harem Series: the books written before the Harem Series that take place in the same world.

It’s about a swordswoman whose student is captured, so she goes to rescue her.

The paramount existences among daemons are known as ‘Great Sages’.

A young man leaves the mountain village and wanders the world, entering the legends step by step, becoming a part of mythology itself.