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 and a trusted advisor to Elsa.

Early life and career
Kai was born in the kingdom of Snoob, where he grew up alongside his brother Karl. At some undetermined time he left Snoob and came to the service of the Arendelle royal court.

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 intentional mispronunciation.

Later, Kai skated in the courtyard with a handmaid.

Christmas
Kai helped to prepare for the Christmas season in the castle, when he received a surprise visit from Olaf who was hidden in the Christmas tree. He was also present for the ringing of Yule bell by Elsa and Anna to begin the holiday season. Kai was also on hand to aid in the search for Olaf, who was lost in the woods. When they found the snowman, the search party remained in the woods; Elsa conjured a large table made from ice, with Kai being on hand to set the table.

Three years later
Kai was on hand to aid Elsa in the hosting of a gathering of dignitaries at the castle; on a balcony, he informed Elsa that the guests were ready to receive her. Before going inside, Elsa asked him whether he had heard a noise, at which he asked her what noise she had heard. Dismissing it, Elsa went with him inside the castle.

When the spirits were awoken, Kai evacuated to the cliffs just outside of the town with the rest of the citizens. He remained there to await the return of Elsa and Anna. Later, he witnessed a giant wave make its way down the fjord; he celebrated when Elsa appeared just in time to stop the wave from inundating the entire kingdom.

Some time later, Kai was on hand to present Anna in her new role as queen, where she went on to unveil a statue.

Personality
As the chief assistant of Agnarr and his wife, Queen Iduna, Kai was diligent and loyal. When not tending to the king and queen, Kai would act as the caretaker of their daughters, Elsa and Anna. Following Agnarr and Iduna's deaths, Kai would continue to serve Arendelle as Queen Elsa's attendant, and later Queen Anna's.

Kai was known for his strict adherence to royal protocol, bowing down to his employers upon greeting them despite Elsa and Anna constantly insisting him to tone down the formalities. While appearing to be seemingly subservient and emotionless at first, and at times nervous, he did however show a more warmer, relaxed side to his personality, such as whenever he gave Olaf a warm hug, and when he participated in his hometown's festivities alongside his brother, also still remembering the handshake he and Karl did as children. In addition, the royal family views him, and by extension, the other servants, as more of a friend or part of their extended family than a mere employee, as evidenced when the two sisters took the effort of coming to Snoob to reunite him with his brother all in spite of the dangers they faced.

Books

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

Comics

 * Frozen: Reunion Road

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.