The 40 Millimeter Death Knight

What's this? another Isekai? Yeah yeah, I know you're all tired of it, but what if I offer you a protagonist who's a knight with a grenade launcher? Interested? good. Follow the story of Dean the Death Knight as he dies, is reborn, and ventures to save the world from an unknown threat. Will he succeed with the weapon given to him, or will he fall again? Tune in in order to find out.