Realistically it's just a way for Rizu to show how much she's learned about people and work with Nariyuki. Rizu and Nariyuki have nothing to work with other than Sawako.
Uruka has the childhood friend angle
Fumino has her sister/advisor thing which is often used for jokes but can still be used.
Asumi has the fake couple
Sensei has the teacher/student relationship.
Rizu has nothing in general.
Bokuben
Matthew Lewis
Parker Hernandez
I LOVE MISAO!
I LOVE RIZU!
I LOVE SAWAKO!
I LOVE SAWAMOM!
I LOVE MISAO!