From what I remember, the manga was set in a world where the people's magic power was determined by the symbol they were born with. There were four symbols. I think that the weakest symbol was suited for blacksmiths, so let's call it the blacksmith's symbol... So the protagonist was this really smart (or strong) mage who ultimately couldn't get more powerful because he was born with the weakest symbol. So he cast a spell on himself so that he would keep getting reborn until he gets the strongest symbol. But when he finally gets the symbol he wants, he realizes that the world around him has changed. The main protagonist is Mathews I think.
The people now think that the blacksmith's symbol is the most powerful and suited for mages while the actual symbol for mages was considered useless. They also seem to think that wordless magic is weak, and it had to be chanted to be stronger, which is actually the opposite. They also worship this certain man that the protagonist seems to remember as a weak and stupid guy from his original life. Moreover, all the weapons have degraded.
The story starts with how the protagonist is bullied by his brother who thinks he's stronger because he got the blacksmith's mark. But the main easily beats him. Then the main proceeds to go to this magic academy which was considered really weak, and aces all the entrance exams and everyone is shocked that wordless magic is strong.
The next clear thing I remember is them going against a rival academy that's really popular for having powerful guys in a tournament. The main now has a small harem of two girls who are in his team and the opponent is a three boys team. He was completely sweeping the floor with them, when they were suddenly found out to be demons, but he defeated them anyway.