The writer just didn't plan this far ahead guys. You can tell because they never hinted at it. Also most people in this mental state at that age would never tell anyone anyway.
With the way Yeonwoo was feeling guilty over Junhyuk’s leg and the way Junhyuk was treating Yeonwoo, being extremely overprotective to the point that it’s toxic asf, I could easily tell that something serious happened in their past.
The writer just didn't plan this far ahead guys. You can tell because they never hinted at it. Also most people in this mental state at that age would never tell anyone anyway.