Hotel del Luna

They both have reincarnation of characters. Lots of flashbacks and stuff. They both have a mystery vibe.

Both dramas contain references to the moon, and Yeo Jin Goo stars in both dramas (the ML in Hotel Del Luna and the younger version of Kim Soo Hyun in Moon Embracing the Sun).

Hotel Del Luna is very similar to this drama in terms of supernatural and solving cases helping ghosts

Both are high fantasy genre Korean dramas written by Hong Sisters. Hotel Del Luna is modern, AoS is historical fantasy. FLs are used to be assassins before.

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

Both are set in a hotel.
Both have a scene of mystery and suspense.
(SPOILER) Both have a romance that slowly blossoms over time.

recommendations are not just about similarities, so I'll just say (beside be melodramatic) TTON is the drama that got me out of my HDL slump~

In the heart of Seoul stands a mysterious, ancient hotel, managed by the greedy and resentful Jang Man Wol, who has spent a thousand years running it. Bound by a deity to prevent her from self-destructing due to her anger and thirst for revenge, Man Wol’s only chance of freedom lies in letting go of her hatred and finding love. Her eternal curse forces her to serve the bizarre clientele of the hotel. When Goo Chan Sung, a former hotel assistant manager, is forced to take over due to a deal made by his father, he helps manage the hotel’s finances, possibly offering the key to Man Wol’s redemption.

Mistura de romance, fantasia e espíritos. Protagonistas ligados por uma missão do além e sentimentos eternos.