The Heroine and Me, the Side Character

A shy, timid supporting boy always follows quietly behind an energetic, lively heroine. Enemies keep appearing around her, making her stronger and stronger, while more and more people gather by her side.

The boy's presence grows ever fainter, but with help from his best friend, he sets out on an endless path of martial arts training, determined to grow stronger and stay by the girl's side to protect her.