The World's Finest Assassin Gets Reincarnated in Another World as an Aristocrat, Vol. 6 (manga) — Rui Tsukiyo

Lugh challenges the orc general leading the monster horde, but no matter how he kills the demon, a mysterious force negates the damage. Tagging out with Epona, the hero unleashes the full fury of her overwhelming S-rank skill—Berserk!” The full power of the hero is revealed at last, but what ramifications will the battle have on the war against the demons—and on Lugh’s true mission?