Masasuke Murase is a senior scribe and the head of secretarial duties within the Ōoku, the inner chambers of Edo Castle. He is a notably elderly man, already ninety-seven years old by the time of Shogun Tokugawa Yoshimune, meaning he was alive before the outbreak of the redface pox that decimated the male population and upended society. This longevity makes him one of the few people who personally remembers the pre-plague world, including the time when the Ōoku was still a women's quarters and the position of its founder, Lady Kasuga, was held by a woman.

Murase is calm, precise, and deeply knowledgeable about institutional history. He carries out his duties with a quiet, unassuming efficiency, maintaining the daily logbooks that record everything that transpires within the Ōoku. His motivation appears to be a steadfast commitment to preserving accurate records for the shogunate, regardless of how sensitive or world-changing the information might be. He does not seek power or influence; instead, he acts as a caretaker of truth, willing to reveal hidden facts when the current shogun asks direct questions.

His role in the story is primarily that of a keeper and revealer of the past. When Shogun Yoshimune becomes frustrated by administrative inconsistencies, it is Murase who retrieves the crucial logbook known as the Chronicle of the Dying Day. He is the one who first tells Yoshimune that the legendary Lady Kasuga was in fact a woman, a revelation that shatters the shogun's assumptions and prompts her to read the entire chronicle. In the earlier timeline of the third shogun, Iemitsu, Murase is assigned by Lady Kasuga to be the personal attendant of the newly arrived monk Arikoto, helping to settle the reluctant priest into his new life as a retainer within the Ōoku. This earlier assignment shows that Murase has long been a trusted servant of the shogunate, capable of handling sensitive and secretive transitions.

Key relationships include his direct service to Shogun Yoshimune, to whom he provides unimpeachable documentary evidence. He also has a subordinate link to Senior Chamberlain Fujinami, the formal head of the Ōoku in Yoshimune's time. In the Iemitsu-era events, he works under the direction of Lady Kasuga and serves as a caretaker figure for Arikoto. There is no indication of strong personal attachments; Murase relates to others primarily through the lens of official duty.

Over the many decades of his service, Murase does not undergo significant personal change. His character is defined by consistency: he is the bridge between the old world and the new, the silent witness who outlives regimes and retains the facts long after others have forgotten or been misled. His development is more about the gradual, deliberate sharing of his accumulated knowledge rather than any inner transformation.

Notable abilities include his exceptional literacy, his meticulous record-keeping, and his flawless memory. He has complete command of the Ōoku's archival system and the bureaucratic language required to maintain it. His discretion is absolute; he only reveals secrets when directly commanded by the shogun, never offering them unsolicited. His advanced age also makes him a living chronicle, giving him a perspective that no other character possesses.