What kind of title is this?: Manga.
How many volumes are there?: 11 volumes are listed.
How many chapters are there?: 66 chapters are listed.
Where can I read it?: Reading links are listed for VIZ. Check availability in your region.

Synopsis

About Bokurano: Ours

One summer, fifteen kids innocently wander into a nearby seaside cave. There they meet a strange man who invites them to play an exciting new video game. This game, he explains, pits a lone giant robot against a horde of alien invaders. To play the game all they have to do is sign a simple contract. The game stops being fun when the kids find out the true purpose of their pact. (Source: VIZ Media) Note: Includes one extra chapter.

Drama Mecha Psychological Sci-Fi