Y'know, I've been thinking, considering that Yuri- I mean, Lili's spell is named Maou Shou Koh Ken instead of Haou Shou Koh Ken, what if this version of Takuma Sakazaki as his Serious Mr. Karate persona is the demon king? I mean, yeah its a stretch, especially since the change from Maou to Haou is probably didn't have that much importance to it, but considering the setting, a Serious Mr. Karate as the demon king isn't really far fetched, especially since it can be explained that the mask DOES contains the soul or essence of demon king, so this version of Takuma could've just picked it up and use it, thinking it was a magical item or something and then got possessed by the mask.