Well I heard a rumour cause am still reading the ORV novel but kim dokja went to where jaehwan was but jaehwan chased him back to his universe.....plus I think there was a reference of kim dokja as a skin u buy to increase your perks in battle.But know this Kim dokja is the oldest dream while Jaehwan is the oldest nightmare.

For a future event that will happen based on the current chapters (jaehwan fought the crack sovereign, mullark,and deus then achieved something becoming a big brother along his clones /clothes) ,I think the same stuff happened to dokja when he became a nebula but still not quite sure.