The Hero Is Overpowered but Overly Cautious, Vol. 2 (light novel) - Light Tuchihi

The controlled chaos continues as Seiya, Rista, and the Dragonkin quite literally blaze a trail through the S-ranked world Gaeabrande. But when Reaper makes an appearance, Seiya is forced to reveal a tactic that he had planned on saving for the fight against the Demon Lord.