The Snow Kingdom and the Awakening Stars.

Several years have passed since the death of the king, and the throne of the Kingdom of Norn has been left empty for the entire unprecedented time. Ruth, the castle's archivist, was living a somewhat dull life, unable to make use of her natural talent for languages. Then one day, she suddenly received a secret request to become the foreign language teacher for Emil, an unimportant prince who was barely a decoration...? The story between a multilingual archivist and a reclusive prince that will create a revolution for their kingdom and shake the entire peninsula as well!

(Source: Kodansha, translated)