Episode 1: Monokuma vs Koro Sensei (Danganronpa vs Assassination Classroom)
Connections: Both are mysterious animal-themed teachers who push their students to murder (Monokuma pushes his students to kill each other and Koro Sensei pushes his students to kill him). Both are seen as the central antagonists of their series, and are usually seen as carefree. Both have huge smiles on their face, and can switch from silly to serious quickly depending on the situation.
Why I chose this matchup: When I first saw this idea, I absolutely loved it, mainly because of Monokuma being on Death Battle (after all, the closest I have seen a Danganronpa character appear on Death Battle was Nagito Komaeda's guest appearance on Wile E Coyote vs Tom Cat). I immediately thought that Monokuma would win... until I watched Assassination Classroom and learned how overpowered Koro Sensei really is. So I really want to see this fight to finally find out who would win.
Soundtrack name: "Execution of a Monster"
Uses both what Monokuma does best, and what Koro Sensei is usually described as. However, like "Requiem for a Thief", this could refer to both, considering Monokuma's actions in the Danganronpa games
Roots/Bets: Rooting for Monokuma, betting on Koro Sensei