Reincarnated as an Instructor in an Adult Game

Reincarnated as the instructor Raide in an adult R18 game, the protagonist finds himself in the body of a side character who was never meant to be the main focus. This is Raide the instructor’s own story, a side character who has now taken center stage. There will be battles, and there will be plenty of hot and sexy situations too. How will Raide get involved in the main story? — Description from novelcodex.org