The reason behind Song Seung Hun's extreme migraines is revealed.

Episode 16 of 'Doctor Jin', which aired on July 15, reveals the origin of Jin Hyuk's (Song Seung Hun) constant migraines. Jin Hyuk falls into a dangerous situation as he experiences another headache.

Jin Hyuk suddenly experiences another headache and fainted as Kim Byung Hee (Kim Eung Soo) says to him, "It seems as though you and I will continue to meet from our unfortunate fate" because Ji Hyuk saved Ha Eung (Lee Bun Soo)'s life.

Upon seeing this Choon Hong (Lee So Yeon) says, "It's become too big. There is a lump growing inside your head. It's been growing inside your head a long time. It is a lump that exists in people that travel to other worlds. You did not know of its existence because it was so small at first, but it is getting bigger now." He explains the reason behind Jin Hyuk's headaches.

This lump appeared because Jin Hyuk because he saved lives of those that should have died, made medicine he should not have made, and told others about the future. Choon Hong warns, "If the lump gets bigger, you will undoubtedly die in this world and in fact, you will become completely extinct. You may disappear before you return to the world you came from."

She further warns that Jin Hyuk should not play with the past any longer. For Jin Hyuk to survive, history must continue as it was supposed to be without interference.