Shinmai Ossan Bouken-sha, Saikyou paati ni shinu hodo kitae rarete Muteki ni naruShinmai Ossan Boukensha, Saikyou Party ni Shinu hodo Kitaerarete Muteki ni Naru.; 新米オッサン冒険者、最強パーティに死ぬほど鍛えられて無敵になる。; The Middle-Aged Newbie Adventurer, Trained to Death by the Strongest Party, Became Unbeatable; 大叔新人冒险者 被最强小队拼死锻炼后无敌了; 大叔新人冒險者 被最強小隊拼死鍛煉后無敵了; 신참 아재 모험가, 최강 파티에서 죽을 정도로 단련해서 무적이 된다

It is common knowledge that it is best to become an adventurer when you are as young as possible. It is common knowledge that it is best to become an adventurer when you are as young as possible, because the magical power that is the basis of an adventurer's strength will hardly grow if you don't train it while you are young. But this man, Rick Gladiator, who became an adventurer when he was over thirty years old, had the combat power of an S-rank adventurer, the highest rank in the world. In fact, Rick has lived an unimaginable life with the members of the legendary Orihalcon Fist, a party of the continent's strongest adventurers. From dragons to vampires, Rick's fighting prowess, trained by his literally "monster" mentors, allows him to defeat elite adventurers one after another who try to underestimate him. Translated with www.DeepL.com/Translator (free version)