I don't see it as filler, the supporting cast of this series is very good and now it's given more focus, something that the series always lacked but wasn't so necessary, I appreciate it anyway.
But I'm not very convinced by the plot of the gang and the direct approach that Norio wants to give to this problem, Kyo and Anna are involved in this but even so, I don't know what Norio is looking for with this narrative and where she wants to go involving the main couple in this.
I'm a bit worried about not seeing sense in things at the moment, but I trust her.
Created an account just to comment on this, cause it's been driving me crazy how no one is talking about it. The purpose of this arc is to give Ichikawa a goal for his future, either a major or career, which is a big step in his development.
He's always felt inferior to Yamada due to her job and her being so "grown up", so he thought studying hard and getting into a prestigious highschool would make him closer to her (from the study arc). But the previous chapter shows that's not the case, he still feels like Yamada is leaving him behind. Then Momo starts talking about the "path she should take" (her future career) and he suddenly feels motivated to help her and find his own path (the title of the chapter is "I want to find my path").
It's clear this is leading to Ichikawa finally choosing a career, something to seriously strive for, just like Yamada does with modeling/acting. From the context of these past few chapters and Ichikawa's personality, I'd say it's either detective or lawyer, but it could even be something related to music, seeing as he's so happy with his song.
So no, I don't think this arc is "filler".