Sakura exposes Kazuha only calling her by first name without using honorifics

I think there is wrong translation here, cause Japanese do have honorifics and formal language tho, they just don't apply it as age strict as Koreans do. But for example, in the workplace you have to call your more senior and experienced colleagues "senpai" and so on.

You can see here girls gasp when Miho says "Oi, Shinoda" Miyazaki, finger pointing.. - YouTube

Among friends, many Japanese ppl. do not use honorifics - it is very common to use names and even informal nicknames etc. It is a reflection of how close you are…the closer, the less formal etc.