Bokurano

Type: TV Series, 24 episodes
Year: 8 Apr 2007 to 17 Sep 2007
Age rating: R – Mature (violence & profanity)
Summary:
During a summer camp, 15 children, 8 males and 7 females, find a grotto by the sea. Deep within they discover working computers and some electronic equipment, and later the owner, a man called Kokopelli. Kokopelli claimed to be a programmer working on a brand new game, in which a large robot has to defend the Earth against fifteen alien invasions. He persuades the children to test the game and sign a contract. All but one of them signs, barely a moment later they mysteriously awaken on the shore believing what happened was just a dream.
Genres: Drama, Horror, Psychological, Science fiction, Mecha