Theres alot, i mean alot of videos about custom psekai (and many other game) maps, so just yesterday i decided to find the game, and I found it. Long story short, the game name is Sonolus, it's not on any playstore and you can download it on github or their official website...

Sonolus
https://sonolus.com
Servers (official chart and custom charts, respectively):
Official
Custom
How do I get it on my iPhone?
2025-06-03