Chaldea's Strongest Master

I was originally a hero who had transmigrated to another world, but on the way to defeat the Demon Lord, I was unexpectedly engulfed by a brilliant flash of light.

When I woke up, I was in the Nasuverse.

Demon Lord: "Hmph, good thing this teleportation spell still works. Otherwise..."

Yu Chaoxian (protagonist): "I can't believe you, you coward! You don't even have the guts to face me head-on..."