Nari:

Sarang, dear what are you doing?

Sarang:

Nothing mom! I just sat after finishing my dinner.

Nari:

What is Hana doing?

Sarang:

She went with Dad. 

Nari:

Alright! Can you come to my room? I need to discuss something with you.

Sarang:

Okay mom! I'll be there in 5 mins.

_____________________

Finally, you all will know what happened on 1st September. Nari is going to share everything with Sarang.

That is the reason why I just gave the name of Nari's character and not Sarang's parents or Jungkook's dad's name. Those characters weren't important unlike Nari's, and giving unnecessary names will only complicate the story. I hope it's making sense now.