An alternate retelling of the manga. 
It depicts most of the original characters from the anime/manga accompanied by a handful of entirely new ones, but with the same task of piloting Zearth to protect the world at the expense of their own lives. Most of the regular characters also suffered changes in their appearance and background.

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)
 
The extra story Bokurano: Mou Hitotsu no Bokurano (Yet Another Bokurano) ran after the completion of the main story.

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