It’s by Trigger and is a “modern reimagining” of the old show Gridman (known to US audiences as “Superhuman Samurai Syber-Squad”)
Gridman is one of a genre called “tokusatsu” which was basically people dressed in costumes fighting on minature sets to simulate giant mosters and robots fighting in live action (if you ever saw Power Rangers, you are familiar with this technique).
If you are a fan of this kind of giant monster show, this will be amazing for you. Not only do they reference all sorts of monsters and more from the original Gridman, the US Superhuman Samurai Syber-Squad, and the Ultra series (notably, Ultraman is getting a netflix adaptation soon), but the 3D animation they use for the fight scenes actually works incredibly well to capture the feeling that Gridman and his giant monster enemies are suits with actors, just like the old live-action shows used to do.
If, like me, you have only a passing familiarity with these old shows, I still recommend SSSS.Gridman. The character design, acting, music, writing, and directing are all top-notch. I say it’s the “smartest show of last year” for good reason. The plot it tells is surprisingly deep and complex, while ultimately working to drive home a simple message: “You are not alone.”
All in all it’s probably the best work Trigger has done in a long time, and is worth watching for that alone.
I’m happy to explain more but refuse to spoil the show. And not because there’s some crazy plot twist - there isn’t - but instead because it’s so well-constructed that to do so would rob you of the opportunity to think about the show and come to understand its message on your own.