Kai

"Oh, I have a message from the queen: Arendelle will henceforth and forever no longer do business of any sort with Weaseltown."

- Kai informing the Duke of Weselton of Elsa's decision to cut ties with his kingdom

Kai serves as an overseer of Arendelle castle.

Service under Agnarr
After Agnarr ordered a reduction in staff, Kai continued to remain in the castle and helped to carry out the king's orders to close up the castle to the outside world.

Ten years later, he aided Agnarr and Iduna with their luggage as they prepared to depart for a two-week voyage and was present at the docks to see them off. However, the king and queen died during the voyage, prompting Kai and a handmaid to drape a black veil over a portrait of the royals in mourning.

Coronation day
Three years later, Elsa was ready to assume the throne, and Kai was on hand to assist with her coronation. He went to rouse Anna, and during the coronation party, he stood by Elsa's throne in the Great Hall, where he introduced the new queen and her sister; when Anna did not stand in the intended spot beside Elsa, Kai ushered her over to the queen's side. Later on during the party, Kai introduced the Duke of Weselton to the sisters, though he incorrectly pronounced the name of the Duke's kingdom as "Weaseltown", to the diminutive man's annoyance.

Frozen summer
After Elsa revealed her powers and fled the kingdom, Kai was on hand to provide Anna with her horse and a cloak so that she could venture off to retrieve her sister.

When Anna returned a few days later, Kai, Gerda, and a handmaid went to bring her inside the castle. He thanked Kristoff for returning the princess and assured the ice harvester that Anna would be taken to see Hans. Kai and Gerda escorted Anna inside the library to see Hans, who was gathered with the Duke of Weselton and dignitaries. He and the others left to give the couple some privacy.

The Great Thaw
As Elsa thawed out Arendelle, Kai and some servants stood outside in the castle courtyard to watch the spectacle unfold. Once Elsa had restored summer to the kingdom, Kai handled some diplomatic matters; at the docks, he accompanied the French dignitary, who stated his intent of returning Hans to the Southern Isles to face judgement from his twelve brothers. After thanking the dignitary, Kai turned to the Duke of Weselton, who was demanding an audience with Elsa. However, Kai instead broke the news that Elsa had broke off relations with Weaseltown, aggravating the Duke with the mispronunciation.

Later, Kai skated in the courtyard with a handmaid.

Animation

 * Frozen

Books

 * Frozen: Book of the Film
 * All Hail the Queen

Trivia

 * Kai shares the same name as the best friend of Gerda in The Snow Queen by Hans Christian Andersen, upon which Frozen is loosely based.