The powerful ruler of all demons, the Demon King, gets punished by God after rebelling against him. As a result, he loses his precious demon horn. To get it back, he must find the 'Princess of Hell' and together, they must purify 100 evil spirits that lurk in the human world. But can the Demon King betray his demon followers and successfully purify them? And it seems there's another issue at hand... "Why is the Demon King so obsessed with his horn?" That's because, without it, he keeps losing his memories!