There is an irony at the heart of late November 1867 that the participants themselves could not fully see: the man most responsible for what was about to happen was already dead.

Sakamoto Ryōma had been assassinated on November 15, 1867 — by the lunar calendar, his own birthday — at a soy sauce shop inn in Kyoto called the Ōmiya. He was thirty-one years old, a 浪人 (rōnin), a masterless samurai with no official standing in any domain. His killers were almost certainly agents of the Mimawarigumi, a pro-shogunate police organization. The exact identity of the killer remains disputed to this day.

What is not disputed is what Ryōma had built. Years earlier, when the Satsuma and Chōshū domains regarded each other as rivals and their samurai had nearly come to blows at early negotiating sessions, Ryōma had physically interposed himself between the delegates. He carried a message between Satsuma military leaders Saigō Takamori and Ōkubo Toshimichi and Chōshū's Katsura Kogorō — later known as Kido Takayoshi. At Ryōma's suggestion, Satsuma agreed to supply Chōshū with weapons to resist Tokugawa military pressure. The alliance was sealed in a six-point pledge, the Komatsu-Prayer Memorandum, signed at the residence of Satsuma's Komatsu Tatewaki. Ryōma's signature appears as witness — the only physical proof of his role, since he held no official position in either domain.

By January 1866, the 薩長同盟 (Satchō Dōmei) — the Satsuma-Chōshū Alliance — was in force. By late 1867, it was ready to move.

November 9, 1867: Tokugawa Yoshinobu formally tendered his resignation to the Emperor in the act known as 大政奉還 (Taisei Hōkan) — the return of governing power. He was thirty years old. His reasoning was sophisticated: surrender the shogunal title voluntarily, appear magnanimous to the imperial court, then reconstitute Tokugawa authority through a council of great daimyō in which he would be the dominant figure. The strategy required his opponents to play by the rules. On the same day, a secret imperial rescript calling for Yoshinobu's 'slaughter' was obtained — almost certainly orchestrated by the anti-Tokugawa court noble Iwakura Tomomi, who had been exiled from Kyoto for years for anti-shogunate activities and was recalled just in time to help dismantle it.

By November 19, Yoshinobu formally stepped down. By late November, his position was crumbling faster than he realized. The daimyō council mechanism he intended to lead had already shown its weakness months earlier: when he had summoned more than twenty major lords to a preliminary council in June, only five showed up. The great lords had stopped coming to him before he even resigned.

While Yoshinobu waited in Osaka Castle for council invitations, Satsuma and Chōshū troops were moving into Kyoto. Saigō, Ōkubo, Kido, and Iwakura were finalizing the plan: seize the Kyoto Imperial Palace by force, issue an imperial restoration decree, and strip Yoshinobu of his domains and title before he could reconstitute Tokugawa power through any legitimate mechanism.

The plan Ryōma had made possible was reaching its decisive phase exactly when Ryōma was no longer alive to see it. He had spent three years pulling two mortal enemies into an alliance, then been killed ten days before the coup he helped engineer entered its final weeks. His assassins almost certainly did not know — or did not yet understand — that the alliance he brokered was already irreversible.

On January 3, 1868, Satsuma and Chōshū forces occupied the Kyoto Imperial Palace and proclaimed the 王政復古 (Ōsei Fukko) — the Great Return to Imperial Rule. The 265-year Tokugawa shogunate was legally abolished. Yoshinobu found himself exactly where Ryōma had predicted: outmaneuvered and stripped of everything.

The man who held no official title, signed no treaties under his own authority, and died before his revolution succeeded had reshaped the fate of Japan. The warrior's ultimate weapon, it turned out, was not the sword but the deal made in a back room.