Kuro no Eiyuu to Kakedashi Shoujo Kishitai

Reg, who was once called a hero, is coerced by his childhood friend, the queen regent, to help train knight candidates to participate in the Arvest Circle, a battle that will determine the future of the kingdom. However, although each of the lady knight candidates has potential, they are still inexperienced as warriors, and they also have their own personal problems....... Can the former hero Reg and the girls save their country from crisis?

(Source: Dengeki Bunko, translated)