It's part of the Gridman Universe, which needs some explaining.
1993 = Gridman the Hyper Agent (live-action tokusatsu series, 39 episodes). I haven't watched this, but it's all on YouTube and it looks like the usual nonsense for children with kaijuu action scenes and silly costumes. Within that genre, though, I'm sure it's fine.
2018 = SSSS.Gridman (anime sequel, 12 episodes). It's excellent.
2021 = SSSS.Dynazenon (anime sequel that I'm writing about here, 12 episodes). It's okay, but it's letting itself be dragged down by its genre in a way that SSSS.Gridman avoided. (In fairness, genre fans would probably say "embraced" rather than "dragged down" and they wouldn't be wrong.)
2023 = SSSS.Gridman and SSSS.Dynazenon rereleased to cinemas as compilation movies, followed by...
2023 = Gridman Universe, an all-new team-up movie.
I should admit that I'm not a big tokusatsu fan. I've seen a certain amount of the genre and I don't hate it, but I tend to find costumed fight scenes boring (here, mecha, kaijuu, whatever). It's exciting fun for children, basically, whether we're talking about Godzilla kaijuu movies or Power Rangers superheroes. Nothing wrong with that. Fans of this genre would call me crazy as they proclaimed that fight scenes are the greatest.
Underneath, I basically like SSSS.Dynazenon. I'm fine with the cast. I like Minami searching for the truth about her dead sister. Gauma's quite funny. I like the heroes' relationships with their laid-back enemies, going to school together and even inviting each other to the pool. Even the kaijuu themselves end up becoming sympathetic, in some cases, with a cute little kaijuu that made me laugh in ep.8 and the question being raised of whether or not it's okay to kill these things.
Ultimately, though, the show loves kaijuu fight scenes. It doesn't think they need justifying, supporting or tying into the rest of the plot. (Minami's sister, for instance, didn't die for a kaijuu-related reason. It's just a subplot in the background that isn't connected with anything else and is really just a reason for Minami to go around with Yomogi.) Episodes will be building up to macho kaijuu fight scenes with COOL TRANSFORMATIONS!!! (and electric guitar music)... and before long I realised that I found them boring. They're empty. The scenes have no content except BIG SMASH!!! and aren't saying anything about the characters. The ep.12 season finale is building up to fifty hours of kaijuu fighting (in subjective audience time) and I was just waiting for it to be over.
SSSS.Gridman, in contrast, made the genre work. Its kaijuu waiting on the skyline were sinister and its blithely murderous kaijuu summoner was a compelling enemy.
Here, on the other hand, the fights don't seem to matter. The baddies are making kaijuu trouble simply because that's what they do every week and they don't seem that fussed. Nothing changes and nothing has an impact. The kaijuu themselves have wacky powers and do fun stuff, but functionally it's not much different from the 1978 Godzilla cartoon. (I leave it as a reader exercise to decide who's Godzooky.)
This series doesn't even feel complete. I'm expecting the backstory with Gauma's princess to be followed up in the 2023 team-up movie. It's not a bad show, mind you. The characters work fine and I'm still a fan of Studio Trigger (even if this might be their weakest show). I haven't been put off watching the movie or anything. This is, though, an underwhelming series that I can't imagine rewatching.