Assassin Academy (2021)

Both deal with assasins and royalty, though Princess A Little Cute is much more of a comedy than Assassin Academy.

Both are short length dramas with an assassin FL.
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Both dramas have a dark, mysterious vibe, and both FLs are assassins. Many of the characters are hiding secrets.

simular feel. set in a school. there`s mystery, romance and investigation.

Both short length Chinese dramas. FL is an assassin. Strong relationship between leads despite moments of distrust.

While very different plots, both dramas have a female character with two souls/personalities in her body who talks to her other personality in the mirror. Also both have an assassin/shadowy organization in search of something one of the characters' possesses.

Both dramas are historical fantasies with a mystery aspect in which people are being killed in order to try to cure/save someone's life. Both MLs have the power of the cure.

Both focus on assassins, with a bond/romance between two of them, and have open endings. However Assassin Academy is much shorter and lighter.