The Tale of the Forever Game - S6.E1

When Peter gets fed up with his tag-along sister Monica, he speeds up on ahead of her and his friend during their bike ride. They become seperated and Peter finds himself trapped in a place where he's forced to play a mysterious game, and his friend and sister are trapped in the woods until the game is finished. If Peter wins this game, he'll be free to leave. But if he loses, he'll be trapped there forever.