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…