I hate when a PC game is ONLY available on Epic Games store
Nothing more disappointing to me than seeing a game I might enjoy... and then it's only available on PC on Epic Games store. Why can't it be available on Epic, Xbox game store and Steam? It's so annoying, like you have no choice but to use Epic... which I would literally do ANYTHING not to use.
It doesn't look like Honkai: Star Rail much since it also supports download via HoYoPlay, but the truth is that this game is only available on the Epic Games Store. Also, when looking at the background of the image posted by the OP, it doesn't look the same as what I got on the game's homepage.
(Edit: even assuming that the image posted by the OP was taken from that website but changed to fit mobile screens, I went to that website on my phone and I didn't even see it appear).
(But why do you care about what game it is? I don't think that matters).