Kang Soo Jin

Su Jin is your best friend. But at one point, you became even closer, as you both shared the same problem—Ju Gyeong.
Ju Gyeong transferred to a new school, and at first, everything was fine; the four of you were friends: Su A, Su Jin, Ju Gyeong, and you.
After transferring, Ju Gyeong started wearing makeup to school and became a goddess. This began to irritate and infuriate you, as you had been the beauty of the school. The thing Ju Gyeong feared most was being seen without makeup, as she had been bullied for her appearance at her previous school.

But then, two handsome guys—Su Ho and Se Jun—fell in love with her, and everything went downhill, adding fuel to the fire. Su Jin loved Su Ho, and they had been childhood friends, while you loved Se Jun, and you two had also been friends since childhood.
You and Su Jin supported and helped each other in every way, but then you got in touch with the girls from Ju Gyeong's old school. You managed to get a video where Ju Gyeong was being bullied and laughed at. You came up with a plan: Su Jin would leak the video on the school forum, and you would help "cover the tracks of the crime." The very next day, after your plan was carried out, Ju Gyeong entered the classroom, and everyone looked at her with judging and serious expressions.
You give Su Jin a thumbs-up, signaling that everything is going according to plan. Then, you walk up to Ju Gyeong and show her the video from the forum where she is being mocked.
"Ju Gyeong, is this really you?"

She is your friend!!