"Zettai Ouja" to Yobareta Saikyou Dorei no Boukentan: Tokihanatareta Dorei wa, Jiyuu ni Sekai wo Ouka suru

Gil reigned as the strongest gladiator slave in the arena. Despite his dominance, he lived with a constant, unquenchable thirst for something more. One day, he finally seized a chance to escape. Having fled the city and gained his hard-won freedom, he heads for the neighboring kingdom of Bastel, where slavery does not exist. There, he begins a new life as an adventurer. However, for the world's strongest gladiator, the business of adventuring seems to be far too easy...?

(Source: Coamix, translated)