Saikyou Mahoushi no Inton Keikaku - The Alternative

Synopsis

Since he was young, he has been on the frontlines fighting against demons. Active Rank #1, the strongest magician in the world, Alusu is now 16 years old and wishes to retire to a peaceful life. However, the military will not let him go so easily. The military negotiated with Alusu to hide his identity and enroll in a magic academy as a normal student. What will come of Alusu’s retirement plan?