A fan appreciation special movie release on Square Enix's official youtube channel which indicated that Jan 1, 2017 will be the start of a collaboration with Final Fantasy: Brave Exvius, a mobile mmorpg launched in Japan over a year prior.
We see the popular cartoon character Malboro-kun as he hilariously runs away from a monster, when Yama-chan appears and makes short work of the tentacled threat.
Yama-chan is the owner of a bar in the immigrant district in Insomnia, where the Kingsglaive members often go to dine, as we can see in a scene of the film itself. He's known for his dish Malbo Smul, and this time around we get to see how he procures his meat.
Incidentally, Yama-chan's fighting style definitely looks like that of a Glaive, so apparently there is more to him than meets the eye.