Heechul ang Hangeng were bestfriend since they were trainees, despite yhe lack of communication. Heechul always finds a way to interpret hangengs thoughts. They bacame closer since their debut, and they live in the same dorm, but as years go by hangeng became distant heechul got really worried and before he knew it hangeng quit sj without telling anyone. Even their leader leeteuk didn't know why hangeng suddenly quit

Hangeng knew that if he told heechul about everything, how the company treated him,

he will also do the same because they were BEST FRIENDS