In Another World with My Smartphone, Vol. 8 (manga) — Patora Fuyuhara

Up against a Phrase, Touya and his party try a variety of tactics to break their foe's hard shell. But as each of their strikes is repelled without leaving so much as a scratch, it seems they've more than met their match. All looks hopeless until one of Touya's new acquaintances suddenly shows up and destroys the creature without breaking a sweat! Who is this traveler, and what sort of power does he possess…?