Shio

Shizu

Rina

Tsuzuri-senpai gives people nicknames using the first two syllables of their names.

Ka-

Waaaaah- It's fine, you don't have to call my name!!

I'm Shio

Still the same

It sounds to me like I'm in a historical drama

I know where this is going already! I get it!!Tsuzuri would call Kasumi "kasu", which means dregs, junk or scum.