Both MLs are powerful supernatural beings who make a contract/deal with the FL that is supposed to result in destruction (of the world vs. her soul).

Both are sweet and fluffy romances with a college setting, endearing characters, and little to no angst.

Both have a similar fairytale like feel for the first half. Both have scheming rich families, a ML who begins the drama by losing his mother and in the present day storyline has trauma as a result of his childhood, and a magical, flirty, and eccentric FL.

The second half of UL has a very similar plot, pacing, and feel to TLBH - the FLs have a false identity and are sent as the spirited princess of one kingdom to marry the prince of a different kingdom for the sake of a treaty. The two clash at first, but are drawn increasingly closer and fall in love. There is an obsessed SFL within the palace who tries to keep the ML for herself and destroy the FL. Both dramas have political scheming, love triangles, and a happy ending after much hardship.

Very different plots, same vibe. Both have a summer countryside setting with farmers, locals, food, and a warm tone. Both have leads of the same gender - one is a BL with two male leads, the other non romantic/friendship with two female leads.

Both are BLs with a warm, summer-y feel to them, with kind and likeable leads, one of whom falls long before the other.

Both are historical dramas with the leads trapped between forbidden love and the schemes/politics of the court. Both have a palace setting, a creepy dowager empress who preys on much younger men, and an obsessed SML who wants both the throne and the FL. UL ends happily, OAO ends tragically.

Both are tragic historical dramas in which the main couple can't be together and are constantly entangled with the schemes and politics of the palace. Both have an obsessed SML who wants both the throne and the FL. In the end, the ML dies and the FL commits suicide or wills herself to die of her illness in order to join him.

Both are historical dramas with an intelligent and strong FL, a plotting ML, and a tyrannical emperor. Both are set within the palace.

Both are set within a palace with heavy politics, scheming, and a struggle over the throne. Both FLs are assuming the identity of another woman, and the emperor or king becomes tyrannical, killing many around him.

Both are historical mini dramas with an assassin FL who has a past connection the the ML (one saved the other's life) which one has never forgotten. Both FLs enter the ML's household to kill someone.

Both are shorter length dramas with a modern day doctor time traveling to the past and curing the ill ML with her skills.