The Demon King Overrun by Heroes

Read manhwa The Demon King Overrun by Heroes / 마왕인데 용사가 너무 많음
I faithfully followed the ‘Demon King’s Textbook,’ only to be killed by the heroes. You’re telling me that my tower and I were just a hunting ground tailor-made for them? Now that I’ve gained a second chance at life through regression, the hell with that sh*tty Textbook—feed it to the Orcs! This is the survival story of Berge, the screwball(?) Demon King!