Extraordinary You (2019)

The two are high school romance dramas with love triangle and cute female leads ,tall and handsome male leads and pretty love stories .

both have "things not everyone can see" vibe going on, as in the hotel with the ghosts for Hotel Del Luna and the realization of the life outside the comic in Extraordinary You
the link to the past ("past" in EY case being previous story)

and similar ending

They both have high school settings and love triangles. The male leads in both dramas have a simple, child-like, pure adoration for the female lead. However, while Love Alarm has some fantasy elements, Extraordinary You is definitely more fantastical. Extraordinary You is also lighter fare.

Both have super cute big height differences between the main couple. Both couples are students and have a friendship to romance relationship.

The two share the same genres ,while extraordinary you is a fantasy setting ,some scenes give similar vibes and are well developed romantic stories .