Masakatsu Inaba is a key figure in the alternate history of Ōoku: Tanjō - Arikoto・Iemitsu Hen, serving as the unexpected linchpin of a grand deception. He is the son of Lady Kasuga, the formidable overseer of the Ōoku, and originally a daimyo with a wife, Yuki, and children. His background is rooted in loyalty to the Tokugawa clan, which places him at the center of a secret plan when the male Shogun Iemitsu dies of the redface pox. To preserve the illusion of a male ruler and prevent chaos, Lady Kasuga orders Masakatsu to assume the shogun’s identity as a body double. He is officially declared dead from the same disease, and his family is never told the truth. From that point, he lives in a hidden room within Edo Castle, always wearing a hood to conceal his face, and must watch his own family from a distance without ever revealing himself.

His personality is defined by deep duty and stoic self-sacrifice. He bears the enormous burden of impersonating the shogun in public while mourning his lost life and the separation from his wife and children. Despite the pain, he rarely complains; his sense of honor and his loyalty to his mother’s scheme override his personal desires. He takes pride in his role, seeing it as essential for the stability of the realm. His motivations are not ambitious but grounded in obligation: he serves because he believes it is his place, and he remains steadfast even when offered the chance to leave.

The key relationships in his story are both poignant and tragic. With his mother, Lady Kasuga, he shares a relationship of respect and subordination; she devised the plan and expects his absolute obedience. His wife Yuki suspects he is still alive and mourns him, but she is never allowed confirmation. His son Tsuruchiyo, who later takes the name Masanori, grows up believing his father is dead. One of the most emotionally charged moments occurs when Masakatsu, still disguised, meets his son during a formal audience. He speaks to him with hidden tenderness, praising him and instructing him to care for his mother. Later, when his son dies of the redface pox, Masakatsu grieves in isolation, unable to mourn openly. His relationship with the female shogun Chie, who assumes the identity of Iemitsu, evolves from a purely functional arrangement to one of mutual respect. Chie eventually understands his sacrifice and offers him the chance to retire and become a monk, but Masakatsu refuses, choosing to remain in the castle because he is proud of his service and wishes to see it through.

His development arcs from a reluctant participant to a man who fully embraces his fate. Initially, the imposture is forced upon him, and he yearns for his family. Over time, he internalizes the importance of his duty and finds a quiet dignity in his anonymity. He does not seek personal glory or recognition. Instead, his growth is shown in his acceptance of a life lived in shadow, and in his final act of loyalty: after Chie’s death, he commits seppuku (junshi) to follow her, an act that unites him with his deceased son in the afterlife. His abilities are not supernatural but practical: he must perfectly mimic the shogun’s posture, voice, and mannerisms, and he carries out this performance with unwavering composure, even in the most trying circumstances. His physical presence is described as tall and dignified, which aids the deception.

In the story, Masakatsu Inaba serves as a silent, sacrificial pillar supporting the fragile new order. His narrative highlights the human cost of political necessity and the quiet heroism of those who give up their identities for the greater good.