I like the idea in premise but damn if the execution doesn't suck, like why in the hell didn't he just kill the Princess and the King? When he was surrounded and he knew his classmates were cursed why not? He also knows the elite knights aren't on the Royal family's side so if he did take them down he'd have some support, additionally he'd free all his classmates in one fell swoop.
Instead he flees the castle and delves into a dungeon... and then one of the other cursed students accidentally frees 6 students, why stop? Why not destroy the other crystals? You know where they are and you know you can destroy them... so why?
Instead the newly freed students flee the castle and go to another country...
JUST DESTROY THE CRYSTALS! Kill the Royal family and destroy the crystals, you're the strongest being on the entire continent and you're running away to get to level 100 so you can come back and finish the job then?!
Dropped.