Arikoto Madenokoji is a central figure in the story, a man whose life is defined by a profound sense of duty and compassion, even as it is repeatedly reshaped by forces beyond his control. He is born as the handsome third son of an impoverished Kyoto noble family, a position that afforded him privilege but also a clear view of societal suffering. Driven by a desire to help others rather than indulge in courtly life, he makes the conscious choice to abandon his aristocratic status and become a Buddhist monk, a path his father reluctantly allows. His wisdom and kind nature lead him to become the respected Abbot of the temple Keiko-in, where his only aspiration is to improve the lives of those around him.

Arikoto's fate is irrevocably altered when he travels to Edo Castle to pay his respects to the shogun. There, his striking appearance and gentle demeanor catch the eye of Lady Kasuga, the powerful and ruthless Senior Chamberlain of the Ooku, the shogun's inner chambers. Lady Kasuga is determined to make him a concubine for the young shogun, Tokugawa Iemitsu, to secure a male heir. When Arikoto steadfastly refuses to break his monastic vows of celibacy, she resorts to extreme coercion, eventually murdering one of his accompanying monks and a courtesan to force his compliance to save another companion's life. This tragic event ends his life as a monk, and he is forcibly brought into the Ooku as a shogun's attendant, renamed "O-Man" by Iemitsu.

Initially, Arikoto’s existence within the Ooku is one of quiet endurance and isolation. He is met with hostility and scorn from the other male concubines, who view him as an opportunist who sold his body to rise in station. Despite this, his fundamental nature remains one of resilience and unwavering integrity. He endures physical punishment from Iemitsu for questioning her, yet he also defends her against the insults of others, revealing a core of quiet defiance and moral clarity. His motivations shift from simply surviving his imprisonment to understanding and alleviating the suffering he sees around him. He discovers that Iemitsu is not a cruel tyrant by nature but a deeply traumatized young woman, forced into the role of shogun and haunted by a violent past, including the loss of a child. This realization transforms his perspective. He recognizes that she is as much a prisoner of the Ooku as he is, and he decides to sacrifice his own happiness to offer her comfort and stability.

The relationship between Arikoto and Iemitsu is the emotional core of his story. What begins with hostility and fear slowly deepens into a profound and genuine love. Their bond is forged in shared vulnerability, particularly after Iemitsu gives him a cat, which becomes a pretext for her to visit his chambers and reveal her pain. Arikoto becomes her sole confidant and the one person who challenges her cruelty, ultimately becoming the first person to show her true kindness. However, their happiness is not destined to last. After a year, Iemitsu fails to become pregnant, and Lady Kasuga, prioritizing the continuation of the Tokugawa bloodline, forcibly replaces Arikoto with a new concubine who resembles him.

Even in the face of this devastating personal loss, Arikoto’s character is defined by his acceptance and continued devotion to the greater good. He is banned from Iemitsu’s chambers but treats his replacement, Sutezo, with kindness and without resentment. During this period, he adapts to his life in the Ooku in other meaningful ways, mastering swordsmanship and archery. More significantly, he uses his wisdom to mentor the other men, giving lectures that offer them a sense of purpose and organizing cultural events like chrysanthemum viewings, which, while inadvertently fostering extravagance, provides a vital sense of community. His compassion extends even to Lady Kasuga, the architect of his suffering, whom he selflessly tends to when she falls ill, along with other victims of the red-face smallpox plague, risking his own life in the process.

Arikoto’s journey culminates in a unique and historically unprecedented position. On her deathbed, Lady Kasuga entrusts him with the care of the shogun and the Ooku. Arikoto requests Iemitsu to release him from his duties as a concubine, unable to bear seeing the woman he loves with other men. She agrees and appoints him as the Senior Chamberlain of the Ooku, a role of immense administrative power previously held only by women like Lady Kasuga. In this role, he restructures the inner chambers and governs all the men within. He remains Iemitsu’s most trusted advisor and closest companion until her early death at the age of 27, where her final wish is for him to guide her young daughter, the future shogun Ietsuna, as a father would. Arikoto dedicates the rest of his long life to fulfilling this promise, serving as a stabilizing advisor and, after a period of leaving the Ooku to return to monastic life under a new name, later supporting subsequent shoguns. His name is absent from official records, a consequence of the Ooku's practice of recording concubines by their female names, but his impact on the lineage and the institution itself is profound and lasting.