I'm pretty sure that is end of content, and it will be for a while since they are working on revamping the beginning instead of new content. Which to be fair the start of the game feels like they weren't planning on this game being as long as it is now, as well as the writing improving by leaps and bounds over time.
My take on what some of the story is.
You're getting the timeline a bit convoluted.
Sensei dated Niki and Noriko pined for him. Then Ami's parents died and he vanished on them. Noriko found him later, and began getting lessons from him. this is when Maya entered the picture.
I get really strong Ladyhawke vibes from Maya and Sensei. They can't be together, whatever curse has fallen upon them prevents it.
Context, because not everyone remembers 80s cinema like I do: In Ladyhawke, Matthrew Broderick stars as a young thief who gets caught up in the affairs of a couple doomed to always be together, but never the way they want. She turns into a hawk by day, he turns into a wolf at night, and they see each other in passing only during sunrise and sunset. The film is ultimately about breaking that curse.
From a narrative structure, Sensei has reached the point where the mentor leaves the picture. So Maya not returning is definitely on the table, and her getting reset has been foreshadowed multiple times since the Dorm War.