Premieres sometime in 2024. This is an anime adaptation of a visual novel game. This series will pick up the story from the Phantom Trigger series of games following the events of the previous movie, Grisaia: Phantom Trigger THE ANIMATION - Stargazer. Check out the ANN article for more information. Synopsis of the previous installment in the series from AniList:
While Rena and Maki recover from their injuries, the other SORD members jet off overseas for a school trip. Within moments of their arrival, though, the Mihama gang are pulled into a manhunt for a SORD deserter, assisted by student Sylvia and Velvet of St. Aile’s International School. Tohka’s the star of the show this time round, but she’s wrestling with her own issues - old memories of her parents, and a promise to a friend that she wasn’t able to keep…
The VNs go like this:
Original Trilogy:
The Fruit of Grisaia -> The Labyrinth of Grisaia -> The Eden of Grisaia
They all got anime adaptations with the same names. I hear they are a fun watch but cut a LOT of content, in particular from the first game (12 episodes for a VN with an average length of 75h on VNDB).
Phantom Trigger:
Grisaia: Phantom Trigger Vol. 1 -> Vol. 2 -> Vol. 3 -> Vol. 4 -> Vol. 5 -> Vol. 5.5 -> Vol. 6 -> Vol. 7 -> Vol. 8
Takes place in the same universe but it’s an indepentent story, it only contains a few references to the original trilogy.
From the descriptions on Anilist, I believe the first movie adapted the first two volumes of the VN, and the second movie adapted the third volume.
Thank you! I updated the text of the post accordingly. I don’t really do VNs generally, so this is helpful.