Prior to the events of the first episode of Despair Arc, Imposter met Ryota Mitarai when the latter collapsed outside of his room. Imposter took care of him and, after doing research on Ryota, introduced himself and revealed his backstory. With the real Byakuya Togami soon going to attend Hope's Peak Academy, the Imposter needed a new identity. The two made a deal so that Mitarai would be able to continue skipping classes in order to focus on working on his anime, while the Imposter would attend classes disguised as him.
As shown in some episodes, Imposter constantly visits Ryota in his room and brings him food. In the ending credits, he is also seen making phone calls, most likely asking Ryota about how to impersonate certain aspects of him or asking about his health.
After Ryota neglects his health by overworking, Imposter brings the Ultimate Nurse, Mikan Tsumiki, to nurse him back to health and shares their secret with her. Later, he also tells Ryota to go to hospital, which eventually leads the latter to meet Junko Enoshima.
Imposter is worried about his friend after his disappearance and informs Mikan about it.
In Hope Arc, Imposter, along with the other classmates and Hajime Hinata, comforts Ryota and tells him to join their group in their atonement for their sins. Ryota is moved by his classmates' forgiveness of his unintentional involvement in the Tragedy, to the point of falling in tears and crying on Imposter's shoulders.
The two are later seen leaving the building together and spending time together on a ship, where Ryota recalls Imposter's old phrase about only being able to trust fats and sugars.
In the bonus mode of New Danganronpa V3: Killing Harmony, in one event, Imposter brings Hifumi Yamada to Mikan Tsumiki after the Ultimate Fanfic Creator was overworking on his doujins. Imposter comments that he had a similar experience with his another friend, meaning that he and Ryota have similar friendship in the timeline of this bonus mode as well, with the only exception being that the Imposter still keeps impersonating Byakuya Togami.
The friendship between the Ultimate Imposter and Ryota Mitarai is one of the most well received things about Danganronpa 3: The End of Hope's Peak Academy.
- Mitworai/Ryotwo is also the nickname for the Ultimate Imposter in Ryota Mitarai's disguise.