The schools has started again after the long summer vacation and all of the the Chou and Yoo kids goes for the same school owned by Mina and Chaeyoung, Heejin's parents.

It's the fifth day of school and Yujin has been strolling around the library for almost an hour now, searching for the Biology science book that she was tasked to find for their group project as the professor instructed.

Yujin was flipping the pages of a book when the sound of someone bickering and tearing papers came from behind the next shelf, Yujin carefully placed the book she was flipping on the shelf before walking towards the mext shelf to check who it is only to see her two sisters, Ryujin and Jimin.

Yujin gasped in surprise and her sisters looked up from the book they are holding, mirroring the same suprised expression formed on Yujin's face.

"What the heck are you two doing here?" Yujin's whispered, marching towards Jimin and Ryujin who quickly hid the book they were reading. "Hello sis" Ryujin greeted with her eye smile while Karina also did the same, following what Ryujin is doing.

"Answer my question what the heck are you two doing here unnies?" Yujin crossed her hands, giving them  a stern look. "Well as the school troublemakers we thought it would be a good thing to visit the library at least once a year to keep our reputation you know." Ryujin answered, flipping her short hair making few strands collide with Jimin's face. "Damn you smell like a dead rat Ryujin!" Jimin whisper shouted making Ryujin shot a glare at her.

"Oh shut up unnies and tell me the truth and how the heck can you two gain reputation as the school troublemakers by coming to the library?" Yujin's brows furrowed when Ryujin just slumped her shoulders and took out the book she was hiding.

"She's trying to learn about you know.. haha how to get intimate with her girlfriend" Jimin explained with a low chuckle, "You came to the library to find out about that? There's no such books in here, You could have just asked it from our moms you know" Yujin boldly stated making her sisters gasp.

"You want us to sleep on the porch for a week?" Jimin hissed at Yujin, imagining how their moms would react if they ask about something like that. "Well you guys can just search it online you know stop wasting your time like this, and I'm sure the librarian must have had a heart attack to see you two in here"

Yujin scolded them but Ryujin didn't mind about the complaints and flip the book before tearing up another page before placing it on the shelf like nothing happened. "Damn you two better stop vandalising the library!"

"Yeah yeah anyway what are you doing here Yuj? Your tutoring class is starting after school not now" Jimin asked Yujin who's eyeing the shelf up and down. "I'm here to find a biology book but still can't find it" 

"Well baby sister we know that we are dumb but never knew you are dumber than us, why would you search for a biological book in the physics section Yujin" Jimin couldn't believe that Yujin did something brainless like that, while Ryujin couldn't help but to burst out laughing, not forgetting to cover to not to make a sound since they are at the library.

" I didn't thought about that, I'm going now bye unnies please leave before the librarian could have another heart attack by seeing what you two have done." Yujin quickly left, leaving the duo there. "Little sissy has lost all her brain cells." 

Meanwhile in the the physics section in the library Minju is trying to reach the book on the top of the shelf, she hissed when she lost her balance from tip toeing but didn't fell down on the floor. Minju looked around, trying to spot a stool so she could climb on it and get the book but no avail, not a stool or even anyone else so she could ask them to help her.

Minju gave up on trying to find help and tip toed again, trying to reach the