Haku starts his palace career as an attendant to a twelve year-old Hotohori. He is the only person who truly understands and empathizes with Hotohori's intrigue with the Priestess of Suzaku, as he is the one who first tells him the Legend of Suzaku and explains that the prince's mark of the "serpent" signifies his identity as a Celestial Warrior. As a reward for his devotion, Haku is made an advisor to the Emperor.
But news of Hotohori's celestial density drives Empress Motaiko to take special precautions to protect her son, isolating him even more after the Emperor's death. Haku takes pity on the child turns into a supportive father-figure and a trustworthy friend for the young prince to confide in.
Time passes and Haku is appointed to Prime Minister on account of his loyalty to the royal family. The promotion comes after Empress Motaiko executes Prime Minister Sai on suspicions of treason. But Haku's new position increases his anxiety and, as people inside the palace become tangled in a political web, he grows into a more cautious, compulsive man.
When the Empress passes away, Haku makes a point to parent and guide Hotohori in the right direction after he is crowned the new Emperor of Konan. With Haku's advice, the Emperor starts in on reforms to insure his country's prosperity, quickly gaining favor in the public and inner court. He continues to be Hotohori's devout supporter throughout the series and carries out his role of Prime Minister with efficiency and care.
- "The Priestess of Suzaku is supposed to come from another world, perhaps she will not even be human. And once she summons Suzaku, she is fated to return to her world. She will never be able to be your Empress, so please forget that notion."
- —Haku to Hotohori
Haku is first introduced in Hotohori's light novel in Chapter 1 in the palace throne room. The Prime Minister reports on the peaceful and prospering Konan to the Emperor. Notes that he, too, is also at peace and then recalls his anxiety under Empress Motaiko's rule. Hotohori gently reminds him not to speak ill of his mother and Haku changes the subject. He comments on his loneliness, suggesting that he start looking for an Empress.
Hotohori claims he has no intentions of following in his father's footsteps by spending all of his time in the Imperial Harem and he will never find a woman as beautiful as he is. The Emperor then mentions the Priestess of Suzaku as a contender and Haku begs him to forget about the legend, upsetting Hotohori. The Prime Minister leaves with a new job: to find a woman that will draw the young Emperor's attention away from the Priestess.
- "Your majesty is eighteen. It is time to consider marriage."
- —Haku to Hotohori, Chapter 5
Haku's role as Prime Minister functions in the background of the original series. In the manga, he is first seen in Chapter 3 inside the Emperor's throne room after Miaka and Tamahome are thrown in the dungeons. He asks Hotohori why he has not sentenced them to death yet and suspects Miaka is an evil spirit. When Hotohori discloses he believes she is the Priestess of Suzaku, Haku is surprised. After Miaka and Tamahome attempt to escape, Haku calls the rest of the advisors to the throne room where he witnesses Miaka accept the role of the Priestess.
In Chapter 5, Haku, Hotohori, and another advisor traverse the palace grounds at night. Haku brings up the topic of marriage and stresses that eighteen is an optimal if not late age to find a bride. But Hotohori claims he would much rather focus on the current state of the Konan empire, much to Haku's dismay. He tries once more and suggests Nuriko as a possible candidate, adding that the newly-found warrior has been released from the inner court and harem to serve Miaka. Hotohori refuses, stating it would be improper to court a fellow warrior before Suzaku is summoned. Sensing his discomfort, Haku reassures him that he knows that his ideal woman is the priestess, validating his feelings, before they are interrupted by the priestess herself. Miaka cheerfully explains she is looking for Nuriko's earring. Hotohori offers to order Nuriko to be kinder but she declines and heads off into the garden.
In Chapter 7, before Hotohori, Miaka, Nuriko, Tamahome depart for Mt. Taikyoku, Haku suggests bringing guards along with them for protection. Hotohori politely declines, expressing his desire to see Konan from a commoner's perspective, and leaves the palace in his care.
Haku is not seen again until Chapter 12. Inside Hotohori's throne room, Haku and the other advisors disclose their growing anxieties about Kutou's hostilities towards Konan. Suddenly, the room is filled with red light and Miaka appears, falling on top of Hotohori, who takes the opportunity to disband the meeting for the time-being.
Nuriko, after being dispatched with Miaka to find Tamahome, returns to the palace in Chapter 15. He meets Hotohori inside the throne room and explains Miaka has gone to Kutou in search of her friend, Yui. Hotohori impulsively orders for a servant to fetch his horse but Haku stays his hand, warning him that the act of an Emperor crossing into hostile territory is grounds for war. He suggests sending soldiers to search for her up until the border and Hotohori reluctantly agrees.
Haku does not appear again in the series.