Shukahime no Omeshi Hito Kakute Itoshiki, Nisemono Miko

A Japanese-style fantasy about a girl with a secret about her birth and a lonely second prince!

"No one must ever find out..." Following a promise to her mother, Hotaru lives hiding the fact that she is descended from the previous emperor. She was treated like a servant in her uncle's house, but one day she is chosen to become Shukahime, a shrine maiden serving the inner god. Shukahime lives in the emperor's palace, and the second prince becomes her attendant, caring for and guarding her. Hotaru is bewildered by her unfamiliar life, being doted on by the coldly beautiful prince, Hiiragi, but she is forced to confront an unexpected secret...

(Source: Shueisha, translated)