"Unnie, i didnt know you secretly write letters for Sinb before?" Yuju teasingly asked her sister

  "I didnt,  it was just one time" Yerin answered

"But Sinb said you have been sending her letters for a month" Yuju said

"Its not my letters, its someone else. I happen to use it on my advantage because I really like Sinb a lot"   Yerin confessed

"What? How? What did you do Unnie?"  Yuju asked confusely

     Yerin started talking about that day she saw Sowon putting the letter, how she took and hide it somewhere and write a letter for Sinb as a replacement of Sowon's letter.

  "So thats the reason why Sinb finally agrees to date you because she thought you are the one writing to her? Which is actually Sowon unnie?" Yuju asked

  Yerin just embarassingly nod..

Yuju finally realize the situation and her very own sister has done something bad to her girlfriend's sister.

Yuju herself is lost in thoughts..

"Yuju please keep this a secret to anyone, I dont want to lose Sinb" Yerin pleaded

Yuju as a little sister she is just nodded reassuring her sister of the secret.

After Yerin disappeared at her sight she was surprise to see her girlfriend glaring at her.

"Did she somehow heard everything?" Yuju thought

"Arent you going to say something to me m dear"? Umji asked

Even if Umji overhead everything, she just want to confirm it with Yuju herself.

"Nothing" Y