Imouto ga Onna Kishi Gakuen ni Nyuugaku Shitara Nazeka Kyuukoku no Eiyuu ni Narimashita. Boku ga.

A younger sister enrolls in a prestigious all-female knight academy and performs exceptionally well in all areas. She claims her brother is far stronger than she is, though he considers himself average. Unaware of his true abilities, he is challenged to a sparring match by the academy's top knight. After the match, he helps her with a massage, drawing admiration from others. His actions also catch the attention of the princess. Despite his belief in his ordinariness, he becomes the center of attention from several female knights.