Seigo no Outei to Maken no Kishihime: Aoyuki no Chronicle

It was an era where a language structure known as the Sacred Tongue allowed one to overwrite the laws of the world like magic—. Young man, Aoi Karen Bradford, was the younger brother of the strongest Sacred Knight in history, as well as an exceptionally talented user of the Sacred Tongue. However, due to a certain reason, he got careless during the entrance exam and received an average grade, entering Sylvius Academy as a normal student and leading life there inconspicuously. Despite being shunned by his peers, he lives peacefully being followed around by the valedictorian of his cohort and childhood friend, Hinohara Yukine, in addition to the exchange student who holds one-sided feelings for him, Carolina. However, a certain incident led to Aoi and Yukine taking on a top-secret mission…? Source: KADOKAWA