Bokurano

One summer, fifteen kids-eight boys and seven girls-stumble upon a hidden sea cave during camp. Inside, they find strange computers and electronic gear, and soon meet the cave's owner, a man named Kokopelli. He introduces himself as a programmer developing a new game where a giant robot must protect Earth from fifteen alien attacks. After convincing the group to test the game, all but one child sign a contract. Moments later, they wake up on the shore, thinking the whole thing was just a dream.