Now I'm a Demon Lord! Happily Ever After with Monster Girls in My Dungeon: Volume 4

Reborn as a demon lord in another world, Yuki's living his best dungeon life! Things are more laid back than ever now that he's returned from the royal capital. Or not-because the Dragon King, Gyuohga, shows up out of nowhere with his sights set on Lefi. 'Become my mate!' he demands. This sends Yuki into a frenzy, challenging the Dragon King to a one-on-one fight! But Yuki's got more than just that to contend with. A demon appears before him with a request: 'I'd like you to meet the king of the demon world.' Intrigued by the idea of being a tourist in the demon world, Yuki accepts the invitation and heads off. What awaits him there, however, is a man with a pretty face and an incredibly shady smile...