2.5D stage plays are indeed a real thing. They originated in Japan and spread to a few other Asian countries over the years, but they're almost unknown in the West (a few of those shows have been performed in Europe and the US, but only recently). I won't give out too many explanations simply because S2 will explain what they are and how they work in greater detail already.
Speaking of S2, while we don't know when it will air yet (we only know it's gonna be in 2024), its release date could be either Summer or, more likely, Fall, so I believe it will start around October.