You need to spend time with Fumiko or Satsuki, during different times of the day.
Talk to Fumiko, if time doesn't advance, talk to Satsuki. If time doesn't advance. Go to your room and skip time there. Then repeat again with both Fumiko and Satsuki.
You know you're doing it correctly if time advances (ex. morning > afternoon).
It's not that complicated. Just spend time with them at different times of the day.