This is my opinion...I know it may seem unfair but for me the writer that write this story perhaps have different views about pararel universe and time travel.
I compare it to the flash who use concept of ime travel and pararel universe which is very good.
In the beginning it was interesting...specially kwak si yang as min hyuk since i like him frim the era wgm with kim so yeon. But it becomes weird and confusing for me...i have no problem with the actors and they did a good job but i am so confused with the cocept of the writer...is he trying to use time travel in the same universe or is he trying to mixed it woth pararel universe...or probably the poor translation that made me confused....seeing tae yi in the past and future and present admiting as they are different but then the will face the same event in the prophecy make me confuse...suddenly there is a to version of each character of bad and good...it did not solified the effect of wormhole or blackhole because the baby from the future was born and raised in the past...and why does it took so long for the writer to unite father and son..even until ep 14...gin gyeom still have no clue that his father was mjn hyuk...i mean...why is he more giving a vibe of rimance between a woman with the mom's face ...it is siçk...unless gin gyeom have mother complex sindrom which just not possible since he has a mental problem regarding his emotionless...i mean there is no info to help me as an audience to understand the background timeline....gosh...it has a lot of potential but if you are used to see the flash and like it ..believe me you wilk compliant like me..but if you are here because of kwak si yang and joo won...very recommended but just donot analyse...overall the cast is really good specially kwak si yang...his aura is different...if you watch wgm him with kim so yeon....so different....he is so manly ???...and he does not appeared much but he shines the same as the lead.....nice acting ???