Bokurano

A group of fifteen summer campers discover a little cave close to the shore while having a pleasant time together. Deep within its caverns, the trio discovers a mystery room where they encounter a strange guy they come to know as Kokopelli. The father invites the kids to join him in a game where they take turns commanding a robot to defend Earth from aliens. All of the kids, with the exception of one, sign a contract committing to play, thinking it may be an amusing computer game. Later on that day, the enormous robot physically manifests, and the kids are transferred inside of it. There, they meet Kokopelli and watch as he leads a battle against a nearby instance of a similar robotic creature. The youngsters are whisked back to the ground in the middle of the mayhem as Kokopelli attempts to apologize after winning the war. The children are left terrified and perplexed as the confusion that followed the brawl begins to fade. The kids had no idea the stakes of this game or how their prior experiences would affect their choices in the future, despite the fact that it initially appeared to be a harmless game.