I quite enjoyed most of it, but Bela gets surprisingly little to do, there's no connection with its parent show and the ending's disappointing. It's still a moderately interesting series, though, and above-average for Japanese live-action TV.
Once upon a time, there was a clever girl called Sasaki Kozue. She fell off the school roof last month. She's dead now... but there's a transfer student called Bela in her class. This "Bela" likes singing the Youkai Ningen Bem theme song, is usually mute and acts more like a lizard on its hind legs than a human being. (That theme song is the only mention of Bem or Belo, while this show's Bela may or may not have a bespoke origin story. Personally, in this show's universe, I think Youkai Ningen Bem is an old TV show, from which this new Bela took a name and a song.)
The show's about schoolgirl bullies. Some of them are openly evil, while another (Shiori) was Kozue's best friend but couldn't go against the stronger girls. She's a bit like the Vichy regime under Nazis. If they threaten her, she'll follow their orders and then get all depressed and weird about it.
I like Bela, who's strange and off-putting. She's bad at human interaction, is liable to encourage bad people and could be mistaken for someone with bits of her brain missing. She hardly ever, though, does anything. One by one, grotesque tragedies befall everyone who bullied Kozue... and I think we're meant to assume that Bela is somehow responsible, but it's unclear how.
The bullies' stories can be gross. They generally end in Grand Guignol and can be pretty messed up even before that. Rin's antics in eps.3-4 are so vile and stupid that I didn't find the episodes easy to sit through. You're going to get caught, Rin. Inevitably. Someone will check the internet shopping history of this old lady you're supposedly doing volunteer work to help. Considering her crushingly trivial motivations, you'll be begging for the worst possible horror ending for her. (This happens.) Schoolgirl prostitution is chosen as a money-spinning option by two of our anti-heroines, although in neither case do things go as expected. It's horror. Forget Bela. She mostly just loiters in the background. For the most part, this show is a linked anthology of two-parters in which horrible schoolgirls make ever-worsening choices and meet gruesome ends.
I disagree with the finale's choices. Shiori's backstory feels implausible (that level of horror on top of everything else?) and it makes her psychology and motivations less interesting dramatically.
Apparently, there's an associated 2020 live-action movie starring the same actress ("emma") as Bela. There are web pages listing its cast and crew... but I've been unable to find the film itself. Maybe it never got released, due to COVID lockdown?
Do I like this show? Not sure. I respect it. The acting has conviction and the tone's unflinching. There will be blood. Disgusting things will be pushed in the viewers' faces and you'll be repelled, which is what the show intends. That's not the same as liking it, though. "Like" is a big word. It's definitely an interesting contribution to the Youkai Ningen Bem franchise, though.