LittleEmber

Ashok Kumar Maurya, a hardcore gamer, is shocked to find himself transmigrated to the world of his recent Open-World game. But the real surprise comes when he discovers his new body isn't any of the familiar characters he once controlled.

The owner of this body is some exiled noble named Adlet. An Extra. An UNKNOWN THIRD-RATE EXTRA. 

Ashok is greeted by the "System," which reveals he was chosen for his perfect game ending. However, due to angering the God of Fate with vulgarities, he’s stuck with an insignificant body. As a result, the System gives him a quest from the God of Fate to preserve his life.

[Main Quest: Achieve the Best Perfect Ending again.
Reward for Success: Any wish, including returning to the previous world.
Failure or Rejection: Death.]

Just because a Quest is assigned to me, does that mean I must perform well in the role I'm given, that of a Third-rate Extra?

With all the knowledge I possess, I refuse to settle for the role of a Third rate Extra, so I chose a new path for myself—the role of a VILLAIN. After all, playing the Hero would only end up in repeating what I did in the game, which is far too boring.

However, to fully embrace this new role, I must rid myself of the old one. To do so, I sacrificed the System and original Adlet's soul to the HIDDEN FINAL BOSS, who is a beautiful Goddess.
……………. 
Follow the journey of Ashok, or the new Adlet, an unknown extra, into a true Villain. Armed with his knowledge of the game world, Ashok uses it as his weapon to overpower the original main characters and even challenge the Gods themselves, carving his path to power and domination with a loving goddess by his side.
................
>>>>HAREM: YES
>>>>Detailed Plot: YES
>>>> NTR: NO
>>>> System: Sacrificed

Note: This book would not be solely focused on the Academy but also the World

Reminder of Talent (7)