Gqux and CSM Part 2 are entirely different stories but Nyaan and Asa are shit characters for the exact same reason
Nyaan/Asa is set up as the secondary MC, and then her entire character goes out the window to revolve around a love triangle with another girl (Machu/Yoru) for a guy she's barely talked to (Shuji/Denji).
The story tries to pretend that Asa/Nyaan has an important relationship with Yoru/Machu, except Asa/Nyaan is entirely defined by Denji/Shuji. Asa/Nyaan had an interesting background which had a ton of potential for great development, but all of that potential was wasted for a shit-tier romance plot because that’s obviously more important than character development