Here's how to fix Nyaan
>Make it more clear in episode 7 that Nyaan is acting out of survival instinct and wants to run away because of her trauma, rather than because she wants to steal Shuji
>After episode 8 Nyaan is miserable because she regrets abandoning the other two.
>Show more of how she is getting all the luxury from Kycillia she never had but she can't stop thinking how she just wanted to share a mundane happiness with Machu and Shuuji.
>Make her think that Machu doesn't need her anymore when she hears that she went to earth alone.
>Her goal of getting Shuji back via Zeknova is now because she is trying to force the trio back together because she knows Machu will be looking for Shuji.
>Actually have her question Kycillia's devotion to her, while also getting closer to her. She should acknowledge she is being used but she should still find her comforting.
>Give Machu at least one moment of realization that Nyaan straight up disappeared and make it impossible for them to just contact each other. They both had their phones, doesn't make sense for Machu to not just message her with "Where the fuck are you?". For all Machu knew, she could've died in the terrorist attack.
>Actually have her confront Machu with her feelings of desperation of trying to reunite with both of them instead of being "I don't know", so Machu is forced to acknowledge Nyaan's situation.
>Give Nyaan and Shuji at least a final dialogue.
I feel like this is what they were trying to set up and then just cut all the vital story beats of it because fuck your MCs, need more nostalgiabait.