That's because the world was created that way

Unknown is rubbing off on me, time to subtweet Karen.

Joking aside, one of the best things The Perverted Prince and The Cat Without a Smile has is how it treats its own side cast. I'd say something about how everybody has their own agency... but it's not really about that, anymore. 

I tend to fawn over how FUNA's works have all of the characters clearly demonstrate their agency. But, in the end, it's one story. Average Abilities is about the story of Mile. The others are part of it, and freely shape it to their own liking... but when the story is eventually over, it's over with Mile.

 

Yokodera, on the other hand, "won" Tsukiko's smile in the end of volume 11. Out of 13 volumes.

This in fact demonstrates two things:

- Sagara is more than willing to let the main characters focus on themselves and their own problems if the situation calls for that. And indeed, the situation very much did not leave them any other choice. All other choices were tried and were failed and were looped over.

- Sagara is more than willing to do the side cast the justice it needs, writing above and beyond for them in what he himself calls "epilogue". 

In fact, Sagara floored me several times in said "epilogue". I knew some loose ends needed tying... but Sagara had much more in store for me than just these loose ends. It's the diametrically opposite treatment than Toradora's "oh yeah, the side cast is fine now". Yes, this is the "subtweet Karen" part.

But yeah, besides all of the characters being human beings (the heroes were all properly reformed to not be heroes) who have it in them to be selfish... it's also that all of the characters in the end had their own stories. The stories interact with each other, of course, but all of the stories were given proper development and proper time to see the result. And what a result it was for some of the side cast! When I reached the actual epilogue, the last chapter of the 13th volume, I could not possibly have called that that's where some of the characters will end up: Azuki and the Steel King, especially.

What's more... yes, there's more!... yeah, it's explainable that Youto is one focal point that brings the cast together. Yeah, it's explainable that Tsukiko is kind of another such focal point. But then we have MaiMai. MaiMai is absolutely just a side cast that really starts having a role from volume 6 onwards. This doesn't stop her from also being a focal point. For example she brings in Cozy-sama - yet another of the greatest additions to a cast that I've seen in my life. In fact, she's most likely who kept the group of four girls together as a focal point in the redone history. And do note that MaiMai gets introduced through the Steel King, not through somebody else. She has her own harem ambitions and love stories, not really that related to Youto. In fact he never really interacts with her love stories in any way besides observing them. Explainable, considering how she never goes after Tsukiko. She's a main character. Not in the "everybody is a main character" hollow ringing ways of some series. She is just the one to sway those around her and to decide her own fate. She just wasn't the one to save Tsukushi.

This is beyond "side characters have agency". At this point the cliche story structure doesn't really exist anymore. 

That being said, it's absolutely hilarious how the main plot of the entire series is "the onee-san is constantly overly spoiled by the guy and the imouto". Even more so when MaiMai has to lampshade how they are continuing to spoil her even in the epilogue.