Armor Hero: The Return of the Underworld

(No harem, no invincibility, focus on character development, not mindless, no system, no clichés, no wish-fulfillment story; proceed with caution if you mind these elements.) [The beginning might not be very good; the first chapter is about the protagonist's development, while the second chapter, "Earth Defense War," has received good reviews.] College student Mo Fan accidentally finds a peculiar stone while hiking. That very night, Mo Fan is transported to the world of Armor Hero?! And he becomes a Netherworld Demon?! A Netherworld Demon currently being sealed away! When he wakes up, the sky has fallen! Just then, the stone breaks Mo Fan's seal… Fine! God, you made me a Netherworld Demon, then I'll be a villain for you to see! Mo Fan finds Kula, who possesses Shadow Master, and stirs up trouble…