Spoiler
To meet Hanako, you need to go to a rumored place where Tess tells you after becoming a sidekick and hide for a long time. Like the actual urban legend, there is a place where you can enter by knocking on the door three times. If you wait patiently after hiding, you will hear Hanako's tiny laugh. After hearing the laughter three times...In my case, I proceeded without catching a ghost, I’m not sure if this event is triggered even after catching a ghost.