The Hero Is Overpowered But Overly Cautious, Vol. 4 (manga)

Will Seiya's… "unique" methods stretch a new ally to the breaking point?! No sooner have Seiya and his friends made it back from Dragon Village than it's time for them to face a new enemy— the Demon Lord's army's Aerial Assault Flies! These absurdly fast-flying monsters might be the most dangerous foes they have faced yet—and to make matters worse, the beautiful but hot-headed Rosalie, captain of the Roseguard Imperial Knights, is raring to charge in without a plan. Can Seiya squash these bugs before this underpowered but overly reckless knight gets herself killed?!

Volume 4 of The Hero Is Overpowered but Overly Cautious manga series by Koyuki Koyuki.