This is the episode that lets you just hang out in Heights Alliance, no villains, no stakes, nobody bleeding. Class 1-A is stuck inside in the dead of winter, bored out of their skulls, and then Mirio Togata kicks the door in with a card game the support course cooked up, because of course the third-year with the biggest grin in the building is the one who shows up uninvited with a box of cardboard. What sells it is placement: this sits right before the Endeavor Internship arc, so you're watching these kids goof off knowing exactly what's coming for them, and it makes the dumb trash talk over card draws land completely differently. The support kids built the thing, so naturally it does more than a card game should. Filler is the wrong word for it. It's a dorm night with people you've watched grow up.

Class 1-A is stuck indoors at Heights Alliance in the middle of winter, restless and bored while they are banned from going outside. That's when third-year Mirio Togata turns up unannounced with something unexpected: a card game called Yuuei Heroes Battle, made by the support class. What starts as a way to kill time becomes something far more competitive as the students pick their cards and throw themselves into heated matches. The game may hold more than it first appears, and the question is who will come out on top. Set just before the Endeavor Internship arc, this single OVA episode mixes action, comedy and slice-of-life dorm fun.