They are two really different dramas, but I also agree that they have things in common.
In Cherry Magic the protagonist is still a virgin at 30.
In Rinko-san wa shite mitai the protagonist is still a virgin at 27.
They both have no experience in love and both, after some doubts, fall in love with their colleagues.

in both dramas the female protagonists are virgins, with no sentimental experience. And in both dramas the protagonists are colleagues.

In both dramas the female lead is ill. And in both dramas the male protagonist accidentally finds her notebook.

Both dramas take place during the school years. In 1 / 100,000 she is ill with ALS, while in I give my first love to you he has heart disease.

Both dramas take place during the school years. In 1 / 100,000 she is ill with ALS, while in I give my first love to you he has heart disease.

Even though the protagonists are of completely different ages, in both dramas, the male protagonists want to continue to stand next to their love suffering from a degenerative disease.

In both dramas the two protagonists meet, have similar interests, fall in love and move in together.

Both dramas are about a female student who falls in love with her professor.
Entrambi i drama parla di una studentessa che si innamora del proprio professore.

Both the protagonists of the two dramas meet by pure chance a person with a beautiful voice who will enter their lives.

Both female protagonists are able to go back in time to the Goryeo era. Here they will meet their love.

Both protagonists are two high school students. In Splash Splash LOVE, the female protagonist arrives in the Joseon Kingdom thanks to a puddle. In Tinted with You the male protagonist arrives in a feudal era by means of a painting. They will both meet a crown prince and fall in love.

both protagonists of the drama manage to go back in time and give love advice to their young selves.