The son of respected samurai Shiba Tonomo, Ibuka was trained by his father alongside his sister Shiba Atsuko. Although he became a skilled swordsman, he was afflicted with a pathological condition that made him prone to cowardice. While bringing back a cow for the feast, Ibuka and Atsuko were ambushed by bandits. Ibuka was left paralyzed by fear and only survived the encounter due to her sister killing the bandits who tried to rape her. He eventually went back home with his sister, without ever mentioning the incident.
Encounter with the Assassins and Templars
As the Boshin War spread to the rest of Japan, Ibuka enlisted in the Tokugawa army to defend the samurai tradition from the Imperial forces who were secretly backed by the Templars to spread their ideology to the masses through rapid modernization and Westernization of the country. Unbeknownst to Ibuka, her sister Atsuko had disguised herself as a male ashigaru soldier in the shogunate forces so she watch over him to ensure that he wasn't killed in battle. During an assault on the camp of British Templar William Lloyd, He witnessed Atsuko fend off "Masajiro", secretly the Assassin spy Matsuo, and his cowardice unintentionally allowed both Atsuko and her Assassin mentor Nakano Takeko to recover the Musashi Masamune, the legendary sword of rōnin Miyamoto Musashi that was owned by the incompetent Saigo Kayano before he was killed. Luckily for Ibuka, since no one except Atsuko and Takeko saw his cowardice, he was branded a hero to the forces of the Tokugawa shogunate.
Afterward, Takeko blackmailed Ibuka and Atsuko into poisoning the wells of Fushimi, a small town that lay in-between Osaka and Kyoto. Posing as a peddler, he and his sister infiltrated the town but she refused to poison to accomplish their mission since she sympathized with several denizens of Fushimi. By contrast, he would carry out the task for Takeko while Atsuko slept. Eventually she discovered that Ibuka poisoned the wells of Fushimi. Atsuko would eventually leave him to join with her ashigaru battalion, vowing never to see or help him ever again. Later, Ibuka would join the personal guard of Matsudaira Katamori, a powerful daimyō from the Aizu domain.
Fighting for the Shogunate
Ibuka was present at the Battle of Toba–Fushimi, however he chose to flee the battlefield and not participate. One of Katamori's men, a samurai named Uesugi threatened to expose him for cowardice. Luckily for Ibuka, Uesugi was crushed to death by a cannonball when he was about to kill his sister Atsuko. However, he later discovered that his father was dead and it broke his bond with Atsuko, after she had pledged to protect his reputation.
Despite their strained relationship, Ibuka would participate in the Battle of Aizu in spite of being rather nervous. In a moment of courage, he would save Atsuko from being killed by Lloyd and eventually slew him. Ibuka carried Atsuko away from the battlefield but he eventually succumbed to his wounds and died.