Tomo Sakagawa is a Japanese Assassin who posed as "Dr. Florent Carpentier" in the Clinique des Rameaux in Switzerland, where the amnesiac Elisa Adler was sent by her parents, Alice and Thomas Adler, following her car accident in the Pyrenees. His goal was to find and have his revenge on Maxime Gorm, the Templar who led the assault teams on the Assassins during the Great Purge and killed his mother Yuri.
Tomo was the son of Yuri, the overseer of the Japanese Brotherhood of Assassins' training camp on the Island of Kyushu before the Great Purge. Despite being raised among Assassins, Tomo wasn't given any martial training, as his mother didn't wanted him to become a killer and opposed Osaka, believing that in order to face the Templars, a modern Brotherhood needed less warriors and more scientists, as she intended her son to be. Consequently, Tomo was regularly mocked by the other children, who had a more traditional training.
In 2000, as Tomo was playing nearby, Hajime Shimada was talking with Yuri about ordering an immediate evacuation and joining with their brethens in Osaka, after informing her about Daniel Cross's betrayal and the beginning of the Great Purge. It was too late, as the Templars, led by Maxime Gorm, suddenly launched their attack on the camp with Yuri being hit by several bullets as she was still arguing with her lover. With her last breath, she implored Hajime to save her son and the two fled in the mountains as the Templars slaughtered everyone in the camp. While Gorm sent the Epsilon Team after them, Hajime somehow succeeded to bring the boy to safety and they later settled in Tokyo.
By 2017, a now independent Tomo had become proficient in computer science and hacking, working in the amusement arcade hall of Mr. Takanori, while searching every databases for clues on Gorm's whereabouts during his spare time. In July, Tomo eventually discovered that Gorm was last seen in Switzerland.
In October, Tomo started posing as a doctor named Florent Carpentier and took on the amnesiac Elisa Adler as his patient. Adler's parents, Thomas and Alice, were two rogue Abstergo employees named who had kidnapped Maxime Gorm. Tomo seduced the young woman and convinced her that a surprise visit to her parents in Madrid was a good idea, as being surrounded by people who loved her was the best way to recover her memories. As the Adlers were arguing about Elisa's presence in Madrid, Thomas noticed the looks between his daughter and Tomo, before Gorm suddenly appeared in the living room.
To Elisa's shock, the young man revealed that he was also an amnesiac, and that he had been kidnapped by the Adlers to be experimented on in their basement. While the Adlers were trying to explain themselves to their daughter, Tomo made a quick call to the Brotherhood to let them know that he found Gorm and that he was proceeding with the elimination. Tomo threw a knife toward Gorm, but the knife instead hit Thomas in the chest, killing him instantly. As he moved toward Elisa, Alice jumped on him and begged Gorm to protect her daughter before the Assassin stabbed her brain with his Hidden Blade.
Later, Assassins reinforcements arrived to the Adlers' house, only to find a heavily injured Carpentier with a knife in his eye and that the two young amnesiacs had fled with the Adlers' research on the Bleeding Effect.