Kunon the Sorcerer Can See, Vol. 3 (manga)

Now that Kunon’s magic tool, the glass eye, is a success, the newly-sighted Kunon decides to enroll in magic school and throw himself even further into his studies! He takes a serious interest in both his peers and instructors, starting with Reyes, a priestess and light mage. But before he can join the advanced class, Kunon must face the dreaded entrance exams.