The dramas have similar time travel principles - they use single world rather than parallel worlds, meaning when something gets changed in the past, it causes a ripple effect in present time rather than creating a new, diverging timeline. Because of this, the dramas reminded me of each other a lot. The romance and angst is also at a similar level.
Both dramas are written by the same screenwriter, both involve a male lead being entangled into supernatural events in which he needs to unravel mysteries to get him and/or his loved ones out of trouble. Both are about escaping from fate in an attempt to manipulate certain rules or principles that bind the supernatural events.
Time travel and romance in both dramas! However, the lead in Nine uses time travel more purposefully to uncover secrets in the past which sometimes makes huge riffles and changes to his present, while Tomorrow seems to be more about traveling to the future and trying to affect it by changing the present. Nine has also a more serious/darker undertone to it.
