Somehow Leon (from Pokémon) and Zoro (from one piece) got lost in the demon slayer universe. They ran into Inosuke who got lost during a mission because he didn't follow Tanjiro and Zenitsu. Zoro and Inosuke started fighting about who's stronger and Leon is trying to stop the fight when suddenly a demon appeared and started attacking them.

Inosuke: A DEMON!! gets our his two swords THAT MEANS A STRONG OPPONENT Zoro: he gets out his swords What is this thing? Leon: Why do you guys have swords? Especially that 15 year old boy Zoro: No idea