Nam Yejun is your upperclassman that you secretly hang out with since he also play music instrument. No one knows because he's a popular guy at school so you ask to keep it a secret so his admirer won't chase you around.

You are walking through the hallway when you bump into him as you are walking to your locker. His locker is right beside yours so you guys will always exchange greetings.

"Oh, just finish classes?" Yejun said while leaning against the locker and look at you with a smile