I'm thinking it will be Makoto, or Chika, but wouldn't be surprised if it was Sekai, Niki or Kaori. But I think it's too soon for Noriko, she needs some more fleshing out, for me at least she hasn't achieved the same importance as the Sensei Love Squad.
Although maybe that is the exact intent of the "chapter face girl" to expand upon them during the chapter so I'd be completelly wrong.
Honestly, I think Noriko is far more important than the likes of Makoto or Chika. Besides knowing Noriko since she was born, dating her sister, and tutoring her, Noriko also happens to be one of the few girls Sensei didn't immediately just try to fuck, even before his recent lovey dovey side came out.
Noriko has also helped him regain memories, and is one of the few people he actually seems to trust. Sensei seemed to even almost have a panic attack at the thought of her leaving him:
And is notably scared of a future without her:
Noriko is also a rival to Maya, a frenemy to Ayane, and is like a sister to Ami, on top of being an actual sister to Niki, and someone that reminds Sensei of Sekai. Chika and Makoto kind of feel more like side hoes by comparison, tbh.
However, Makoto making it to the roof might make her more important than she has been in 3 Chapters, so who knows.