Training With The Demon King

Story:

The cold-blooded Demon King, unparalleled under the heavens, lost all his abilities to a crude trick by a female Hero. What is this magic ritual that requires you to give mouth to mouth with a person of the opposite sex? Even I, the Demon King was bested by this oddly suspicious attack?! But no worries, I can always regain my abilities. Even if you’re a succubus, an elf, a beastwomen or the noble hero’s descendant. As long as I can use you to further my cultivation, I will. In order to revive the glory of the Demon Race, this magic called the “Cultivation of Yin and Yang”, I’ll learnt it and show you!