It's literally just Isekai. The only twist is when he died, he just respawned back into his own already magical world. (Korea/Japan but with magic and monsters). Also I have no idea where this tension you're talking about is, literally every episode after the first, the protagonist just wins. No struggle whatsoever, no conflict, nothing. Just w after w, which is the worst part about most isekais.

Boring as hell story. Pretty animation though.