I didn't say they would be completely uninvolved but the ideas I've been seeing float around is that "next is Kanade5 and then we get Ena and Mafuyu events about this" which I think is setting yourself up for disappointment. This is nothing like the Mafuyu arc and if anything.. (gestures at the first year of the game) that was the actual Mizuki arc with a year of buildup. Ena's Picnic event is centered around her bond with Mizuki and desire to reach out, Mizuki's heavy involvement in Carnation, the final scraps of buildup in Mirage of Lights and the end with the zinger that is Footprints. Doesn't that sound familiar to you...?
Kanade and Mafuyu will certainly play some sort of role as do most characters in most events, but it will almost definitely not be anywhere to this level of how personal Mafuyu's arc went and it will probably be more with Ena than it is with Mizuki. That is what I am trying to say. The game even cracks a joke on the player about how Kanade and Mafuyu are unaware of what is going on (there is an area conversation between the two that is just them lightheartedly talking about the festival and how they hope Ena and Mizuki are having fun. It's framed in a specific way that hurts to read as they don't know what we know).

As for Mizuki's friends at Kamikou--well, the problem is, Mizuki is infamously known for skipping class. Toya and Akito will probably not even bat an eye to Mizuki's absence. An has a similar deal in that while she's closer to Mizuki, she also knows Mizuki is a terminal class skipper... that, and the two are in separate classes now and the writing team just weirdly never wants to acknowledge them. They have by far some of the least outward content of any Y1 classmates and it took them until the very last event before the age-up to even give them a class event together. One of my biggest gripes tbh.
I do very much agree Rui will have some sort of content with Mizuki--a side story at minimum, AFTER Mizuki and Ena work things out together feels extremely realistic. Maybe even this next Niigo event. I am hoping to see this, personally! It makes a lot of sense Rui would have a follow-up considering as you said, he knows Mizuki's intentions.

I'm not actually a particularly big shipper. You can see that I do not list anything in my carrd, because it's not really that important to me. So, I'm not saying this because of desiring "ship content" or a bias in that sense. I care about the narrative of the story as someone who reads pretty much every nugget of content from events to menu lines to area convos to side stories to interviews the developers have offered, and have been interested in the game for around 3.5 years now. I think writing people you disagree with off as "shippers who ONLY want content to themself" is weird and says more about the type of person you are, honestly. I notice this happens a lot to Mizuki and Ena in particular, which is interesting. Why do people hate the idea that they have a specific bond and narrative unique to them so much?

Anyways, I'd love to talk to you again on November 30th, Anon. I think it could be nice to see how our predictions pan out. Will I be wrong? Will you be wrong? Who knows.