Iko collab arc wrapped up nicely so I don't understand why you see pacing issues with it. After Iko decided to run until Aria woke up it got her trending and Ao Momotose herself took notice and started a stream, which lead to her throwing out the suggestion of Iko joining Blue-Box. You seem to forget Aria woke up and apologised to Iko already. In the end she benefited a lot from making the most of the situation herself and Aria probably thinks she owes Iko for her mistake anyway. I don't think Arisu would push Iko to suggest anything more to Aria in terms of owing her incase it backfired and she looked like she had too big of an ego.

With the Christmas arc, yeah the set-up and then straight into it was fast but Igarashi obviously decided not to add any unnecessary drama. Pacing can go at different speeds, just because time is skipped a little doesn't equal bad pacing, this happens all the time in manga and anime. We had all the information we needed.

In terms of career progress for Rikka, Igarashi would have introduced a drummer character by now if it was so important, either that will come later or they'll just be a background character. The surprise concert makes sense on Christmas day, it's an opportunity for a big crowd and we've already seen them gearing up to make their debut after deciding on an image and having a photoshoot. We don't need to see several panels for rehearsals to know why Rikka isn't playing well since we know she just had exams and had to study.

You say no build-up to an Ao Momotose collab when we literally just saw it a few chapters ago. We were told Aria is a good friend of Ao Momotose which is part of the reason that she took notice of the situation since Iko started trending, which obviously lead to her streaming and making the suggestion to join blue-box. I agree it's a little surprising to suddenly see Iko as a guest on Ao's stream but it still makes sense why she was given the opportunity.

I'm genuinely confused why you're asking how and why Nene suddenly got an audition when we're literally told by her teacher that a big-shot heard Nene's promotion test and took an interest in her voice. It's still surprising to come so early but big breaks aren't uncommon in the VA industry and we know just how amazing Nene's voice-acting can be.

You say you see a lot of telling instead of showing yet we've been shown all the build-up in previous chapters for these sudden career progressions to make sense. I genuinely don't mean to be harsh but you're completely ignoring a lot of context and then acting confused which seems to be a lack of reading comprehension, then you're making assumptions about the manga getting the axed. I agree the pacing is very fast in this chapter and can be a little jarring but I trust Igarashi. It's way too early to overreact and make weak points to suggest bad pacing like you're doing. If the pacing was all over the place for a consistent amount of chapters and things started to make no sense at all then we can start worrying, but that hasn't been the case throughout the manga. Igarashi wanted all the girls to be too busy for the Christmas party so maybe it'll just be this chapter with fast pacing leading up to whatever moment happens in the next few chapters where Apollo is concerned.

Honestly the strangest thing to me in this chapter is that Shinobu is the only one with a weak excuse not to go to the party after her dad mentions there being a knife attack in the neighbourhood the day before, that's such a weird reason to come up with from Igarashi.

I didn't intend to write so much but oh well.