year 1997 - when both of them were 6 years old 

" Good morning, class " The teacher suddenly came in and the students quickly ran towards the seats and stand behind their chairs.
" Good Morning, Ms Bae " The class answered their teacher. 
" Sit down everyone " Her statement made the class to sat down and paid attention to the teacher. 

She then called someone from their door softly and that gesture made the whole class to look at the door. 
Then, here comes a young quiet boy walking into the class and stand besides the teacher, facing the students. 
The teacher pat the young boy's back before talking back to her students. 

" Now, this young boy will join your class. " She looked down at him, nodding to the students, signaling that he should intriduce himself. 
" Annyeong, my name is Yong Junhyung. Please take good care of me. " He said, bowing a little. 

" Yongjun Hyung? Why should we call him hyung? " Suddenly one kid spoke up and all the attention are all to him at the very back in the middle. 

Another young kid who comfortably put his feet onto the table and leaning back towards his chair with his arms behind his head. 

" Sungyeol, behave " The teacher raised her eyebrow waiting for him to put down his feet. 
" Sit down properly. " She continue. 
" Ah, sorry! " He raised his hand and put down his feet with no manner. 
" And this is not Yongjun. His name is Junhyung " The teacher finally answered him. 
" Ah. I see. Hey, Junhyung, come sit beside me! " He called Junhyung and pat onto the table besides him. 

Junhyung with no emotion walks towards the table where Sungyeol asked him to go. 
Junhyung sure feeling uneasy about this but he ignored it. 
He sat down when he arrived.
However, with his surprise there is a liquid flowing from his chair making his pants wet. 
He widened his eyes and stood up quickly. 
Sungyeol realized what had happened and started to say " Teacher! Junhyung peed in his pants! " 
That statement of his makes all of the people in the class turn their head to see what had happened and laugh afterwards. 

" Lee Sungyeol! Come with me to the principal office! Junhyung, I am sorry. You can go to the toilet and pick up an extra pants in the locker in the toilet. Singyeol! Come here! " The teacher shot Junhyung an apologetic look. 

She knew this going to happened. 
Sungyeol is one mischivious kid. 
He wouldnt live a day in school without making trouble. 

" Why did you pee'd " He patted Junhyung's shoulder and shook his head, laughing before following the teacher to go outside. 

Junhyung stares at him and clenched his fist tight before letting it go and went to the toilet to change. 

FLASHBACK

Lee Sungyeol went to the school early today just because he thought of some pranks. 
When he arrived at his classroom, he saw no one and sighed in relieved. 
He walks confidently towards the table beside him and took something out from his pocket.
Revealing a liquid mixed of glue and water in a small bottle. 
He let out a small evil laugh while pouring out the liquid onto the chair. 
After he succeed pouring out the liquid, he put his hand on his waist and laugh evilly. 
He then realized that it was too early when he saw tha wall clock and walks towards his own place to continue his sleep.