Ilhoon got a sudden anxiety after Eunkwang enlistment hence he reach for Hyunsik to overcome it and seeking help. However, Sungjae being a jealous jerk that make Ilhoon more frustrated.
There are many words that I haven't say.
There are many questions that I haven't ask.
I know we have ended but on the other hand we never really end.
Maybe one day, someday, we can find each other again.
But for now, this is enough.
We were getting farther and farther, but why did not we know?
It is so painful to forget one by two.
(1,2,3 - BTOB)
or
Sungjae and Ilhoon are in pain and Sungjae tries to sort things out.
(also on ao3 and asianfanfics)