Kensei no Osananajimi ga Pawahara de Ore ni Tsuraku Ataru node, Zetsuen shite Henkyou de Makenshi toshite Denaosu Koto ni Shita.

Also known as: 剣聖の幼馴染がパワハラで俺につらく当たるので、絶縁して辺境で魔剣士として出直すことにした

by Gaku Shingyou

Fynn is so distressed by the continuous harassment of his childhood friend Alphine, a swordmaster, that he decides to break off their relationship and goes away to make a fresh start in a frontier city. He changes his appearance and changes his name to Flick to start a new career as adventurer. He has only trained as a sword fighter, but the receptionist at the guild suggests measuring his magic abilities, and it turns out that he has an enormous amount of magical power! Then, Noelia, the daughter of the frontier count, known as the "Infinite Magician," approaches him..... (Source: Futabanet, translated)