The lore used in Girls' Frontline is shared with MICA Team previous game Codename: Bakery Girl, which takes place 30 years after Girls' Frontline. As the story of Girls' Frontline unfolds, it relates more and more to the wider world created by MICA, players should be aware of future spoilers when reading on the expanded world of Girls' Frontline.

Aside from the main stories of the games, the Artbooks and their Confidential Files are the main sources of extended lore. There can also be scattered information in promotional materials. Most of these sources are not officially translated in English but translated by fans.

Quoted from GFL lore wiki

MICA also making GFL: Project Neural Cloud & GFL2 which will expand the lore. Codename: Bakery Girls also getting a remake in English later this year. They are making a GFL shared universe, and plenty of lore to come.