The Ossan Newbie Adventurer, Trained to Death by the Most Powerful Party, Became Invincible manga volume 1 features story by Kiraku Kishima and art by Ken Ogino.

“The early bird catches the worm.” Or so they say. Yet our hero, Rick Gladiator, passed his 30th birthday before taking even his first step as an adventurer. He may just be getting started, but he's already showing S-Rank level powers. His teachers, the legendary party Orichalcum Fist, are monstrously strong (literally—check out the dragon and vampire), and they've put him through a training regimen from hell. Now, Rick faces down the elite adventurers who scoff at him, prepared to teach them a lesson about respecting their elders—and they may just have to learn it the hard way.