Who is Hanazawa Hanako? I was rewatching the first season of Oregairu the other day, and something caught my eye on the list of contacts on Hachiman's phone (which we see in episode 5, after Yui adds herself as a contact).

 

The list here is:


Komachi
Grandpa's
Home
Soubu High School
Takatsu Dentistry
Dad
Barbershop
Hanazawa Hanako (花沢華子)
Mom
✨✨Yui✨✨


So we have Hachiman's relatives; places he goes (school, dentist, barber); and now Yui. But who is Hanazawa Hanako? That's a girl's name - but why would Hachiman have a girl's number in his phone?
Hikigaya asked for a girl's phone number in middle school, as mentioned in his flashback at 6:30 - 7:00 in episode 4. The number probably belongs to her, though he left her anonymous in his story in the anime (I haven't read the early volumes of the LN's). There's no Hanazawa Hanako in Volumes 7-10. For now, she remains in the back-burner of possible characters.