On 17 December 2013, Kiyoshi was guarding the entrance to the headquarters of the Osaka Brotherhood when he was approached by Gavin Banks and Emmanuel Barraza, who demanded to see the head of the Onmoraki-Gumi. Kiyoshi told them to leave before he had to beat them, but Gavin then insulted his fashion sense and refused to go. Kiyoshi responded by punching him in the face and kicking him as he fell to the ground. Several of his fellow Assassins came out to watch and cheer him on, and Kiyoshi attempted to stab Gavin with his Hidden Blade.
However, Emmanuel stuck his palm in between the blade and Gavin, allowing his hand to be impaled. Emmanuel then asked Gavin what the first tenet of the Creed was, stunning Kiyoshi, who responded it was "stay your blade from the flesh of the innocent". Emmanuel pulled out a dog tag with the insignia of the Assassin Order on it, proving he and Gavin were also Assassins. Kiyoshi retracted his Hidden Blade and apologized to Gavin and Emmanuel for attacking them. He later complimented Emmanuel on how he stopped his Hidden Blade, claiming that he was "almost Japanese" in how he dealt with the pain from his impaled palm.
On 31 December, Kiyoshi accompanied his Mentor, Saeko Mochizuki, aboard the Altaïr II to help the crew gather supplies for their next journey, and to celebrate the new year. After sparring for several hours with Emmanuel, Kiyoshi managed to convince Emmanuel to join Dr. Stephanie Chiu and himself at a local karaoke bar.
By late 2015, Kiyoshi was ordered by Saeko to go to China to help the local cells and to look for Álvaro Gramática's secret laboratory in which he planned to replicate an Isu's body with the help of the Shroud.
In 2016, Kiyoshi and Arend Schut Cunningham were sent by Gavin to rescue Galina Voronina and her team from a Templar strike-team assaulting Erudito's hideout in Argentina. With a helicopter, the two Assassins rescued their fellow Assassins and their Erudito allies and also killed the high-ranking Templar Ortega Sanchez while escaping the island.
In February 2017, Kiyoshi and Arend were in London with Galina and her apprentice My'Shell. During a training session, Galina recieved a call from Charlotte de la Cruz, who reported back on her mission in Hong Kong. Charlotte informed her fellow Assassins that the Abstergo office they raided for intel about the Phoenix Project was empty and that Barindra Mitra's cell was butchered by an unidentified third party.
The Phoenix Project
One month later, in a back alley outside of Abstergo offices in Berlin, Kiyoshi, Arend and Galina intercepted Heinrich Hart, a scientist and Kiyoshi's mole within Abstergo. The pair were seeking answers over their losses in Hong Kong and threatened the German because it was his informations that led the Assassins into the ambush. Hart swore that he knew nothing of what had lied in wait for them at the Hong Kong site and told them that the Templars didn't knew what happened too, with rumors that the feared Black Cross was investigating the matter. After demanding that Hart find answers or else they would come back for his blood, Galina and Arend left.
In London, Kiyoshi and his fellow Assassins review the media, where a large explosion in Berlin dominates the headlines. Kiyoshi argues that killing 170 people in public doesn't really fit with the Templar ideals, and suggests another faction might be in play. My'Shell reveals that she has a list of Pieces of Eden retrieved from the Hong Kong Abstergo lab, and pulls up an image of the Koh-i-Noor. With My'Shell convinced that it is present in the Spanish Civil War, Charlotte straps herself into the makeshift Animus. The machine appears to malfunction, with Charlotte seemingly trapped inside a simulation and unable to be woken. An injured Guernica returns to find the team surrounding the stricken Animus. He is shocked to learn that My'Shell has repaired the machine with unvetted Abstergo parts, and fears that the machine is now compromised. She makes her apologies and leaves, whilst Guernica informs the others that they will need the assistance of Felix Oladele - an Abstergo/Erudito plant based in Montreal whom is familiar with Animus extractions.
Kiyoshi and Arend make the flight immediately to Canada, and using a cargo plane perform a halo jump on to the roof of Abstergo Montreal. After working through the few guards present, they reach the office of Oladele - only to find him already slain by a high tech Assassin, the same individual from Hong Kong. The 'Assassin' wounds them both with throwing knives, and throws Arend out the nearest window which he just manages to hang onto. After a few shots from Kiyoshi's gun, the 'Assassin' jumps from the window. Kiyoshi and Arend both make their way back out, both heavily injured. The only way that the 'Assassin' could know where they were headed is if they have a leak either from the Animus or one of their own within the Brotherhood. They then decide to lay low in a safe house.
Back at the safehouse, Kiyoshi and Arend arrived to find Guernica bound to a chair by Galina, whoexplained that she found Guernica attempting to slash Charlotte's throat. She believed that he also sent the both of them to Montreal to die and have been trying to obtain information but to no avail. Arend was unwilling to take part in the torture, so he left to recuperate. Kiyoshi, on the hand, had his doubts as he had experienced the torture before. He asked Galina what information she had obtained, to which she said someone was sifting through the memories of Charlotte in the Animus. Kiyoshi and Charlotte suspected that My'shell may be on the same side as Guernica since they both came from Erudito. After a short while, Charlotte woke up from the Animus, telling both of them that she knows who was attacking them and that they need to warn the Templars.
Sometime later, Kiyoshi discovered Arend, who called the Abstergo Entertainment Customer Service to warn them about the Instruments, who had infiltrated their ranks. As they argue about Arend's actions, Charlotte cuts it to end the conversation. The Assassins were later surprised by My'shell, who had returned with the Templar agent Juhani Otso Berg. At a restaurant, Berg explained to the Kiyoshi and the Assassins about his mission in Geneva, where he met My'shell and was attacked by the Instruments. Kiyoshi told the group that Guernica may be a member of the faction, which My'shell refused to believe. Berg suggested that they work together which Charlotte accepts.
Equipment and skills
Kiyoshi was quite skilled in hand-to-hand combat, being able to best Gavin rather easily, and also showed a proficiency with firearms. Kiyoshi is also credited as a master swordsman as shown as he always carries his sword on missions. When battling Gavin in Japan, Kiyoshi is shown to have a Hidden Blade under his sleeves.