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.