Anna, the fourth princess of the Rain Dukedom and one who holds the power to call forth the rain, travels to the Sun Kingdom to marry Sun King Livius for her country, despite her own reluctance. She soon discovers that the King, who conquered the world in only three years after his ascendance to the throne, is still a child. Furthermore, for trivial reasons, he has demanded that Anna call forth the rain, and when she refuses, he has her thrown in jail. The story follows the two who, while at first are a married couple only in name, gradually begin to establish an emotional bond with one another.
The fourth and youngest princess of the Rain Dukedom and Livius' love interest. She is the main protagonist of the story. She has the power to call forth the rain when she sings. She is sent, against her wishes (and because she lost a game of rock, paper, and scissor against her older sisters), to the Sun Kingdom to marry Sun King Livius so that her country can retain its autonomy. She discovers that the Sun King, who conquered the world in only three years after he ascended to the throne, is still a child. Although, initially distraught by her fate, Nike comes to love Livius and accepts her future as the "Sun Queen".
Optimistic, understanding, and stubborn but caring, Anna quickly gains the affection of the peoples as well as Livius, who clearly loves her. She is said to be more popular than Livius among the people in the Sun Kingdom as she seems to interact with them on regular basis and helps them out when she can. Anna is also very strong, as shown when she beat up four of the palace guards. She will also avenge herself, if she believe that any wrong has been done to her. For example, although Rani originally wanted to kill Anna and almost succeeded in doing so, Anna forgives him, but she also beats him up for carrying out the attempt on her life.
Liviu's is the king of the Sun Kingdom. In the three years following his enthronement he was able to conquer the rest of the world. While he is rumored to be a monster of some sort, he is actually still a child. Although his father was the former king, his mother was a commoner. While she was still alive, the two of them lived an isolated life in the castle because of his mother's low social status. Livius began his campaign to take over the world after his mother's death. He has a loyal butler who seems to understand him.
His abilities as a king are considerable. Not only was he able to cleanse his kingdom's government of corruption soon after his coronation, but he then methodically defeated each opposing nation one by one. Anna has noted that although Livius is just a boy, his eyes are those of an adult. He granted the Rain Dukedom autonomy, but in exchange, he told them to send a princess to become his wife. Anna was sent to him and he is fond of her and grows to love her.
After his mother's death, Livius grew cold and cruel and became distrustful of everyone around him. Neil, his butler, stated that this is because he doesn't know how to reach out to people, a trait he developed because he was constantly surrounded by enemies while growing up. This came about because of his mother's low social status. He and his mother lived a quiet, isolated life in his father's palace and were only able to rely on each other for support. After his mother's death, Livius began to show his true potential and he flourished, not stopping the expansion of his influence until the world was conquered. In a way, his campaign can be seen as a diversion to distract him from the pain of his mother's death.
As the story progress, Anna's presence and efforts to help the young King slowly begin to change him. On several occasion in the series, Livius can be very childish. Livius can also be very protective and violent when people that he cares about are threatened. He didn't hesitate to raise his sword against a person who attacked Anna, although Anna stopped him from killing the man. Later on, Livius reveals that he still harbors a much colder and crueler and if not an extremely jealous side. He imprisoned his uncle Bardwin and confined Nike to her room because he thought that Bardwin had seduced Anna and that she had fallen for Bardwin. He even threatened to burn her home kingdom to ashes, when Anna talked against him for sending Bardwin to prison.
