It reminds me of Made in Abyss. They're both powerful anime, because of children in mortal danger. But, with cases, there's more to it than that.
They're very different shows, though. (The Promised Neverland's original manga has never been accused of sexualising children, for starters.) I always wanted to keep watching Made in Abyss. No matter how gruesome the horror, I always loved and was optimistic for Riko and Reg.
This show, on the other hand, was tough. Trying to marathon it would have been too much for me. It's set in an orphanage, surrounded by trees and overseen by an ever-smiling "Mama" who loves all the children. They depend on her. They're at her mercy, because they're children and she's not. To be in that orphanage is to know that Mama could do anything she liked to you, at any time, and there's nothing anyone could do to stop her.
Our heroes are some of the orphanage's older children. (There's a ceiling of eleven years old. If you reach your twelfth birthday and somehow you haven't yet been shipped out... well, bye-bye.) Emma is the fastest, strongest and most unswervingly compassionate. Norman is the cleverest, but physically weak. Ray is dark, cynical and a bit lazy.
At the start of ep.1, our heroes adore Mama. She's a tireless guardian and looks after them all. No one pays any attention to sinister touches like the tattooed numbers on everyone's necks, as in a concentration camp. Soon, though, they see something bad and realise that they really, really need to escape.
Unfortunately, though, preparation is needed. Under Mama's nose. While living in the house. This show got to me. It's designed to scare the willies out of you, but the show's strength doesn't come from its horrific content (which is rare). No, it'll get to you with nothing more complicated than coming down in the morning for breakfast. Or walking down a hallway. Or having a conversation in the woods. The anime's producers made some controversial changes from the original manga, in particular cutting internal monologues. (Apparently the changes for Season 2 are even more extreme.) Here's a quote from the director, Mamoru Kanbe, when he was asked about that:
KANBE: "The reason why I chose not to use as many monologues was to increase the suspense. In the manga, there are a lot of monologues from Emma and Krone. If we know or hear the monologues we know what each of those characters are thinking and what their intentions are. But instead of finding flat outright as an audience, we only focused on Emma's standpoint and what she knows. We don't know exactly what Isabella or Krone is thinking or their intentions so that increases the tension and suspense because we only know Emma's perspective. How you overcome that suspense is what we wanted to do."
It works. I admire the show, but whew.
There are clever touches. The ep.3 analysis of the children's weak points when playing tag will apply later too, in more horrifying circumstances. The show's also not afraid of comedy. You won't be laughing much, but ep.5 managed it with the children's reaction shots to a certain admission. I also admire the plot device of education, in which the orphanage is trying to train the children's brains and will ship out anyone who keeps failing their regular tests. Thanks to that Darwinian system, anyone who's reached 11 years old will be by definition the smartest children and so can plausibly be this good at planning, hiding and organising.
Also, more fundamentally... the villains. Would you have made the same choice? They're not actually evil, underneath, which just makes the agony worse. Bloody hell.
One possible negative is that some English-speaking fans have talked of racial insensitivity (there's a black baddie with a mildly cartoonish appearance), but I didn't see her character design as out of step with the art style of the show in general.
Avoid all spoilers. You want to know as little as possible. Rewatching this show won't have the power of your first viewing, because you'll know what's coming. Suspense comes from anticipation and possibilities. It's a Schrodinger thing. Open the box and the cat dies. This is a strong series, with an obvious real-world allegory. There's also a live-action film, which I'll definitely be watching even though I'm not expecting much. (They'll make the children older, which by definition will undercut the horror of the premise.)
Strongly recommended. Not everyone will be able to get through it, though.