Similarities between the two drama:
—Cold hearted male leads who at the beginning don't care/don't really like the female lead
—The girl chases the guy first and they live really close to each other

Both are based on Chinese novels
Both are painful but you cannot help yourself but be enthralled by the plot, OST, acting, cinematography and the tragic love of the main leads.
They both have supernatural elements(one less than the other but still)
The supporting characters stories are really interesting and add to the main story

Longing Heart and Reunited worlds are similar in certain points like how they are both time themed drama. Both without much focus on the details on how time was bent
—The school setting is important for the plot
—precious familial ties and moments. The main leads understand how their actions or absence affected their surroundings
—high school first loves

They are obviously cooking themed drama so they both:
— have restaurants settings
—deal with the rivalries and power plays that can happen in a kitchen
—Food food and even more food. Food bringing together our main couple
Also:
—arrogant male leads who have the skills to back it up
—love triangle(sls)
—cold man/warm woman trope

—Paranormal theme for the win.
—The roles are switched but one of the main characters needs the other for their "survival" and takes up a job to be close to them.
— slow burn romance.
—tragic past events shaped their present situations

These two drama:
—deal with the entertainment industry
—have eccentric accomplished male leads who deal with certain health conditions
—the female leads have both a notorious reputation
—the couple goes through various difficulties to be together

The two drama are similar in:
—Eccentric chaebol male lead
—gutsy female lead who is working in the entertainment business
—a "paranormal" event brings them closer
— the secretary/manager are doing an excellent job of being there and always rooting for the main couple
—the secondary couples' stories are also prominent

These two dramas are similar when it comes to the main leads being wrongfully accused of deeds they didn't commit yet took the blame/fall for. How one wrong accusation ruined their life. Finding out the truth over that event is also a similar theme in both drama.

Borh dramas deal with time travel and the attempts of the main lead to change the past/future. The decisions of the main lead are of great importance for the time-related plot and how small changes alter a person's course in life.

Both deal with time as their central theme and the struggle to find out the truth over a past event and how small changes can alter one's life in unexpected ways. Despite the fact that Reunited Worlds focuses on the Past, Tomorrow With You focuses on the future, the feeling they emit is similar