Why, he’s roleplaying. As a [certain character from Yugioh], no less, who would be the creator of Duel Monsters. Could it be you’re unfamiliar with Yugioh?

Speaking of roleplaying, the [particular term Ouma uses for Monokuma] early on is used in tabletop roleplaying- in essence, a fiction all on its own. More to that, Ouma assumes a role akin to the ‘double agent’ in Mafia.

So this mood isn’t terribly weird for him, either. Because…

…he is even excitable like this, during the main mode. During a death game.

What a coincidence, it so happens that you’re playing for your life, and he’s acting more or less the same way, while rigging them for you to win…