Yugo's appearance slowly progresses over the course of the series. Initially, he is seen as a young man with brown hair and light-brown eyes. During the Sunrise and Metal Float arc, Yugo is seen significantly older, sporting a stubbed beard, taller stature, and a more rugged expression.
Yugo is shown to be aggressive and short-tempered, particularly in regards to AI.
Yugo's first hatred for AI was due to the fact that they could perform multiple actions which can be seen as part of their mission. This results in his piano teacher's death, who happened to be an influential AI in Yugo's early life. Because of this, he keeps a white and black key from a piano as a necklace.
Later on, the emergence of Toak, an Anti-AI organization gives vent to his sympathy. This organization aims to remove all the AIs from having the same right and treatment as humans, and Yugo decides to join them, as he is unable to resolve the conflict in his teacher's last words. It is during his time with Toak that he meets Diva, who saves him multiple times throughout the series.
AI Naming Law Arc
Yugo is seen with Toak during his first operation to assassinate Aikawa Youichi. He is trapped inside the building when Matsumoto locked down all the hallways, almost dying after Matsumoto triggers the bombs that have been installed below the construction. However, he is saved by Diva. Yugo is triggered with the fact that he is saved by AI once again upon facing his past. After the assassination fails, the group leaves and Yugo reflects on what happened while holding the collar that his teacher once wore.
Sunrise Fall Arc
The Toak members led by Yugo infiltrate the Sunrise Space Hotel, with the suicide mission to crash the hotel into the ocean and create a foundation for the mistrust towards AIs. He has Elizabeth, an AI he picked up at a waste pile 7 years ago, replace Estella to gain control of the ship. During the process, he recognizes Diva, the AI who saved him 15 years prior, and decides to locate her to get an answer of why she saved him. However, he is unable to do so as Elizabeth injects him with a dose of a sleeping drug, motivated by her wish for him to live on. Yugo wakes up inside an evacuation ship, listening to Estella and Elizabeth's singing as the two of them fall to their demise.
Metal Float Arc
Upon attacking the Metal Float with the objective to shut it down, Yugo and the other members of Toak get attacked by the AIs from the unmanned island. A few members survive, and Yugo once again meets Diva 5 years after the previous Singularity took place. Seeing Diva as just one of the bust AIs who won't follow orders like what he thinks of Elizabeth, he questions her of her true objective, only to get the same response as what he heard from his teacher. Realizing the dire situation they are in, Yugo decides to put conflicts aside and helps her, as they happen to share the same objective this time.
Ophelia's Suicide Arc
A young Yugo can be seen observing Diva's performance at the Zodiac Festival. He is noticed by Diva directly before her performance and subsequently flees the scene, luring Diva into a trap. He appears again during Matsumoto's surveillance of Ophelia, where he is chased down by Diva once more. Yugo proceeds to incapacitate and restrain Diva, injecting her with a virus that gradually deletes the "Diva" personality. His intention with this action is to communicate with Vivy. Matsumoto intervenes and frees Diva from her restraints. A fight occurs soon thereafter between Yugo and Diva, who is assisted by Matsumoto. Yugo is defeated, revealing that he has assimilated into an AI (hence his youthful appearance). Yugo briefly monologues to Diva before passing away, alluding to a greater "Divine Revelation"
- Yugo's surname Kakitani means "hedge, fence" (垣) (kaki) and "valley" (谷) (tani).
- Kakitani's "Divine Revelation" was one of the Archive's adjustments to keep the timeline consistent with the original history.