It drops you into a lights-out prison with zero orientation and dares you to keep up. Nobody gets a name: you get the pleasant young man, the sexy woman, the ex-soldier, the hacker girl, the creepy old man, and a cat, and you start reading them like cards on a table instead of people. That is the trick, because the title is a roulette bet, the five-number bet, famously the worst odds on the wheel, and once that clicks the whole thing rearranges itself. The guards are gone, the exit is gone, and the old man's behavior sets off something the story never bothers to walk you through politely. Yes, the exposition is murky and the characters stay archetypes, but the background art is gorgeous and it moves fast enough that you rewind rather than quit. It plays like a sci-fi short story you finish on a train and think about for a week.

A handful of unusual inmates share an isolated prison: a young man who seems honest and kind, an alluring woman, a middle-aged former soldier, a young hacker girl, a mysterious old man, and a cat. One day a blackout unlocks every cell and sets them all free. Yet the guards have disappeared, and no one can find a way out. When the old man starts behaving bizarrely, something extraordinary happens to the prison and everyone inside it. The single OVA mixes mystery with science fiction.