Grisaia is really a series of visual novels, with a main trilogy of adult games with explicit sex scenes (but also non-porn versions). To date, it's had these anime adaptations:

MAIN TRILOGY = The Fruit of Grisaia (13 episodes, 2014), The Labyrinth of Grisaia (shortish film, 2015) and The Eden of Grisaia (10 episodes, 2015). These feature Yuji Kazami (a government assassin) and his female classmates at Mihama Academy. I quite like them.

PHANTOM TRIGGER = the franchise's first all-ages game, with an all-new cast. No plot links or shared characters. It's supposedly a sequel to the main trilogy, but I couldn't see any connection beyond the school's name (Mihama Academy) and the premise of again being set in a world where the Japanese government has black ops agencies that employ teenage assassins. Schoolgirls are trained in murder and go on missions. To date, this game's anime adaptations are a two-part 2019 movie, a 2020 sequel movie and a 2025 sequel TV series.

I'd already reviewed the Phantom Trigger movies on release, but I rewatched them in preparation for this TV series... which was the right decision, I think. I'd been expecting a reboot, but no. You can regard the movies as episodes 1-3 of a staggered 16-part series. What's more, it's pretty good. Our schoolgirls are indeed assassins and the show's pulling no punches about this. "The target wandered through two hours before schedule, so I got the job done early."

No one studies normal school subjects. It's always sniper practice, physical training, murder techniques and so on. What's more, there are other schools like this. How much state-sponsored wetwork happens in this series's universe? It's also underlined that you're not allowed to consider truth, morality or consequences. If your boss says "kill", you do it. You're not allowed to hesitate, even if the target is your sister, your best friend, or even yourself.

The enemies they'll face are pretty evil and there will be casualties among the protagonists. The tone fits the premise. The girls are likeable, fun and capable of ignoring orders for the sake of rescuing their friends, but there will be a ton of killing and no veils being drawn. We see one girl on the point of suicide, putting a gun to her head. Noble altruists who defiantly save lives can get shot in the head. The last few episodes are a war movie. There will be a traitor. "I'm aware of this. Please dispose of me when I'm no longer needed."

There's one lovable innocent, who's the show's central character and audience surrogate. (It's an ensemble show, but she's the nearest we have to a protagonist.) Arisaka Shiori isn't an assassin and doesn't understand that world. She needs things explained to her. Mihama Academy hired her as a teacher, although I'm not sure why. She's endearing, although she'll be going on a character journey.

Incidentally, the visual novel has good and bad endings. Everyone lives, or everyone dies. The anime goes in between.

The show's universe is dark, unsurprisingly. ("The truth is, a lot of these kids don't live past the age of ten. As their numbers grow, they're pushed into one of two jobs: prostitution or killing.") However, the show itself isn't grim or depressing. They've pulled off a tricky balancing act with the tone. It's fun. There are jokes and the girls can be silly. The show's less fanservicey than the original trilogy (i.e. no tits) but frame compositions sometimes feature bouncing chests. Also, Mihama Academy has a buxom headmistress with a bad personality who greets new teachers in her underwear and says things like, "There's nothing I love more than being an absolute arsehole!"

The secret organisation they work for is called SWORD... er, no, SORD. It's an acronym for Social Ops, Research & Development.

It's pretty good. The original trilogy might be better, possibly, but it's close and I like both. (Also, the original's a harem anime where the male protagonist's female classmates fall in love with him, whereas this is female-led and not about romance.) The original has a smaller, more memorable cast, but I liked the Phantom Trigger cast too. There's a ninja girl with a rebootable memory who doesn't remember her previous personalities, or at one point even her own sister. Grisaia is a decent franchise. It's still going strong after 35 episodes, 3 movies and various specials and I'd happily watch more if they made it.