Saiteihen no Ossan Boukensha. Guild wo Tsuihou Sareru Tokoro de Ima made no Doryoku ga Mukuware, Kyuu ni Saikyou Skill "Mujouken Shouri" wo Eru

Adventurer Louis is nearing forty, yet he remains stuck at E-rank. Mocked by the guild as the “Immovable E,” he is the butt of everyone’s jokes. One day, prepared to face death in battle, Louis somehow manages to defeat a magical beast far stronger than himself. At that moment, his level rises for the first time in his life, and he acquires a skill simultaneously. That skill is 《Unconditional Victory》—said to have once belonged to a legendary hero. A skill that can cut down even the most formidable foes in a single strike… just what is its true nature!?