After dealing with Vieri , Ezio checks on his sister Claudia who was told by uncle Mario to keep track off Monteriggioni's finances in a record book, which infuriated Claudia, who was used to a luxurious lifestyle. Over time, Claudia got used to her new job but missed Ezio while he was journeying around Italy to take down the Templars joined by Izumi who was asked by uncle Mario to serve as mentor for Ezio.
Ezio returned to Florence in to gather information on a conspiracy against the Medici, who had been family friends to the Auditore. However, Ezio chose to visit Cristina first, who was quite surprised to see him. She also admitted that she was to be married, as she thought she would never see Ezio again. Izumi remains outside while Ezio did his thing , when there was a scream outside , that a man named Manfredo was in trouble with several gamblers. Ezio asked who Manfredo was, and Cristina confessed that he was her fiancé. Ezio ran off and found Manfredo in a fight with several gamblers he was indebted to and also Izumi lending a hand to Manfredo.
After defeating the gamblers Manfredo talks to Izumi " thank you "
" Not a problem , if someone needs help you help them "
Izumi turns around to see an enraged Ezio , he then demands that Manfredo be a good husband to Cristina or he would kill him before storming off. Manfredo then eyes Ezio as he walks away " whats his problem ? "
Izumi remains silent saying nothing but knows Ezio is prone to violent outbursts. Ezio then met Cristina in an alleyway afterwards and kissed her, promising that he had made sure her husband would be good to her.
Sometime after Ezio had Leonardo construct him a pair of Hidden Blades with the intent of giving one to his partner Izumi , but Izumi refuses the offer and request only one should be made for Ezio's use favoring the use of her own tools : senbon, surikens , kunais , and the ninjato over the hidden blade showing Leonardo the schematics of her tools since they felt more familiar to her.
" think you can do it ? " she asks.
" yes that should not be too hard "
" thank you " Izumi responds with a bow.
Leonardo then provides some info on the Pazzi conspiracy directing him to find La Volpe , Ezio was able to find La Volpe, who aided him in discovering the Templar conspiracy against the Medici. La Volpe directed Ezio to an underground catacomb where a Templar meeting was being held.
Before he enters the catacomb he tells Izumi to stay behind intending to do this alone. Izumi lets out a sigh " alright , but come back when you are done. "
While she waits she cannot help but notice somethings seem a bit strange a few people were carrying a guan dao then a short distance away was her enemy one of the members that had destroyed her brotherhood in japan her family was able to make it out of Japan but was scattered, but the brotherhood not so lucky. Currently ruling Japan are five members one from each clan known collectively as the five celestial dragons and their grandmaster Zheng Lang a Chinese Templar with plans of expanding their influence to other countries. Izumi at this point lacks the power or the allies to do anything all she can do is sit quietly as the Templars slowly take over her country and China.
Ezio was subsequently able to eavesdrop on the meeting, discovering that the Pazzi planned to kill the Medici at the Basilica di Santa Maria del Fiore and place their own people in government under the orders of their master, Rodrigo Borgia.
The next day Ezio arrived at the Duomo to try and prevent the public assassination, Little did Ezio know that Izumi was watching from the rooftops. Izumi then draws two senbon needles aiming at acupressure points of Francesco de' Pazzi and Bernardo Baroncelli and throws them just as they were about to kill Giuliano de' Medici and injure Lorenzo , incapacitating the two aggressors.
Ezio looks around just as the two people fell to the ground " who gos there ? "
" Relax is me , and lucky I got here fast enough or this can get messy " said a voice Ezio then looks up at one of the rooftops and sees Izumi standing there. However, the Pazzi had already succeeded in their plan, and brought the city into a state of civil war.
" Izumi but how I thought you were busy ? "
Izumi ignores the question and drops down from the roof telling the group " Its not safe here we got to go , there will still be people who are out for your life " After escorting Lorenzo to the safety of his palazzo, Ezio revealed his identity, prompting Lorenzo to remark that he knew Ezio's father. Izumi however did not reveal her identity keeping her hood over her head. Izumi also stands out due to her black colored assassin robe , the lack of a hidden blade on her forearm and a sword that hangs across her back rather than the side like many other local assassins , Izumi looks very much like a ninja.
Lorenzo's lieutenant, Poliziano, told Ezio that Francesco had been sighted at the Piazza della Signoria. As Pazzi and Medici troops battled in the streets below them, Ezio chased down and slew Francesco, although Jacopo de' Pazzi and several other conspirators were able to escape the city.
Ezio desides it is best for Izumi to remain in the city with Lorenzo and Giuliano de' Medici as a bodyguard in case the Templars are still out for his life and in case he is killed and a civil war breaks out. Izumi still does not trust Ezio and believes that his emotions will get the best of him when out alone on the field Assassins are supposed to defend the light not bring the world into darkness.
Shortly afterward, Ezio met up with Lorenzo at the Ponte Vecchio. Lorenzo reminisced that as a child he had fallen into the Arno and would have drowned, had he not been saved by Giovanni Auditore. This act of kindness kindled a close friendship between the Auditore and the Medici families. When Ezio asked of the conspirators, Lorenzo explained that they had fled the city. With this, the Medici publicly cleared the name of the Auditore family, and provided Ezio with the names of the conspirators who had escaped. Learning that the Pazzi conspirators had fled to San Gimignano, after gaining information from Mario, Ezio tracked down and killed Antonio Maffei, Stefano da Bagnone, Bernardo Baroncelli and Francesco Salviati, extracting from each man information on Jacopo de' Pazzi's whereabouts. Using the information, Ezio located his quarry and tracked Jacopo to an ancient Roman theater. Once there, Ezio eavesdropped on a meeting between Jacopo, Rodrigo Borgia and a Venetian merchant and Templar, Emilio Barbarigo. After fatally wounding Jacopo for his failure to capture Florence, Rodrigo revealed that he was aware of Ezio's presence. While Rodrigo and Emilio fled, Ezio was apprehended by Templar guards, but he overpowered and killed them before swiftly putting the dying Jacopo out of his misery.