You're dropped into a card game that is explicitly a war crime, and the show never explains the rules because that's not the point. The animation pivots between hyperreal combat and pure abstraction the moment the game takes over someone's mind. By the time you realize what you're actually watching, a kid has already lost everything to a card that rewrites probability itself.

In the year 20XX, humans known as Concodes pair up as buddies with ultra-capable AI partners called Codeman to battle in the card game ZENOZARD. Its world championship, THE ZENON, has fans in a frenzy. Souta Azuma leads the life of an average high schooler. Then a mysterious woman named Eilietta Lash challenges him to a battle. She turns out to be a Codeman, and she wants Souta as her partner so the two of them can enter THE ZENON. Souta goes along with it, though not eagerly. Their very first opponent is Shion Saionji, a famous player who attends Souta's school, together with her buddy, Ash Claude. Card battles meet action, drama and sci-fi in this single ONA episode.