Byakuya Togami?

The Ultimate Imposter's true appearance features long black hair, thick eyebrows, and green eyes. They have a notably heavy build, yet are capable of flawlessly impersonating others—even when the person they are copying has a completely different physique. Their gender is unknown, but they present a convincingly male persona while disguised as Byakuya, flawlessly mimicking his voice, mannerisms, and poses. There are two instances where the real Ultimate Imposter's voice is showcased. When they reveal their face to their classmates for the first time, they speak with a deep and masculine voice. However, during a game reset sequence at the climax of the Killing School Trip, a brief glimpse of what appears to be their real voice sounds notably different—higher-pitched and more gender-ambiguous.

While disguised as Byakuya, the Imposter closely resembles the original, with blond hair, bright blue eyes, and rectangular white-framed glasses. Their shirt appears identical to the ones worn by the real Byakuya; however, this version of "Byakuya" has a much heavier build and wears a white dinner jacket, white slacks, and white dress shoes.

As an Ultimate Despair, the Imposter—still in their Byakuya disguise—wears night vision goggles emitting a red light from within.

They also impersonate Byakuya in Danganronpa S: Ultimate Summer Camp and wear a recolored version of his swimsuit, consisting of tight-fitting yellow swim trunks with teal and dark gray side accents, paired with an open white zip-up jacket that has matching teal and gold trim.

As Ryota, the Imposter has short, light brown hair, hazel eyes, and rosy cheeks. They wear a Hope's Peak Academy uniform with a green tie.

As Kyosuke, the Imposter has short white hair and dark purple eyes. They wear a white suit that Kyosuke wears during the events of the Final Killing Game.

Since the Imposter can only exist by impersonating others, they develop a distrustful and skeptical personality, unable to talk to others about their past. They describe this lifestyle as a living hell, as it causes them to both distrust others and be distrusted in return. Although they simply want to live a normal life, they believe they can only do so by assuming someone else's appearance—and that they must "disappear" if ever found out. This compels them to seek acknowledgment by impersonating others, plunging them into a constant need for affirmation. According to Chiaki's understanding, the reason the Imposter continues to live a lie is because impersonating others is their talent—they were bound to it from the moment they were born and have no other option but to keep relying on that talent, whether they want that life or not.

Their yearning for acknowledgment is also why the Imposter does not take offense at Hiyoko Saionji, the Ultimate Traditional Dancer's, rude nickname for them—"Mr. Ham Hands." Instead, they appreciate her honesty, as she took the time to observe them and come up with a nickname based on their physique, one of the few traits that remain consistent regardless of their disguise. In their final Free Time Events, the Imposter is pleasantly surprised and relieved when Hajime affirms that, regardless of their true identity or the fact that they are not the real Byakuya, he still considers them a friend and even expresses genuine liking toward them. It's something they've never heard before but always longed for, convincing them that they truly exist, that their existence is absolute, and strengthening their desire to stop living a lie. In the original Japanese, the Imposter in Byakuya's disguise normally addresses everyone as "omae" (おまえ), which is a rude and somewhat egotistical way of saying "you." However, this facade briefly cracks in this particular moment when they address Hajime with "kimi" (きみ), a friendlier, same-level way of saying "you," before reverting back to "omae" at Hajime's request. Until that time comes, they have to keep relying on their talent, which extends not only to appearance but also to the personalities of the people they impersonate. While disguised as Byakuya, they are arrogant, pushy, and condescending. As Ryota, they appear timid, somewhat asocial, and have a workaholic tendency. Both characters closely mirror the behavior of their original counterparts.

There are moments when glimpses of their true personality bleed through the disguise, or when their interpretation of certain traits slightly deviates from those of the person they are impersonating. These instances frequently occur when they are disguised as Byakuya during the Killing School Trip. While the original Byakuya had an "in it for himself" mindset and seldom engaged in group activities until the later stages of his killing game, the Imposter demonstrated exceptional leadership abilities and a strong sense of responsibility from the get-go. Both also have an arrogant demeanor, but their approaches differ greatly. While the real Byakuya's arrogance presents itself as "I'm better than you" with a player-like mindset, the Imposter's arrogance derives from the conviction that "I'm better than you, which is why I must lead you all so none of you die." It is also revealed that their skeptical nature drives them to take their promise of ensuring no one dies under their leadership seriously. This leads them to organize an all-night party without informing anyone that it's to protect them from a potential murder. Even though they see this trait as a burden for most of their life, they deem it, for once, to be of good use during the killing game—an essential for survival at all costs.

The Imposter's desire to assume leadership originates from their interpretation of Byakuya's past. They admire him as the "most absolute existence" because of his underdog story, defeating hundreds of his siblings to claim the title of Ultimate Affluent Progeny and lead the Togami Corporation. They interpret Byakuya's rise to power as a proof that if he were in a Killing Game, as a superior being he would be naturally inclined to the role of a leader who can unify others under his guidance. In line with this interpretation, Sonia notes that the Imposter is trying to fulfill (what they believe to be Byakuya's) destiny—to stand above others through sheer will and commanding presence—by faithfully emulating his leadership qualities. Though compatible with Byakuya's hubris, this perspective fails to reflect the actual impact of his upbringing. The need to defeat so many siblings made him disdainful of teamwork, cold, self-centered and imbued with a sense of superiority. In contrast to the Imposter's idealized view, the original Byakuya values self-reliance above all else and refuses to cooperate, believing his superiority places him above such efforts, as demonstrated throughout the Killing School Life. As a result, the Imposter adopts Byakuya's condescension, self-confidence, narcissism, and overwhelming presence—so much so that Hajime dubs them the "Ultimate Affluent Protagonist." Yet they don't come across as a bad person; as Hajime frequently notes, their calmness under pressure and composed demeanor make them someone the group can rely on.

The Imposter's compassionate, selfless, and caring nature are what ultimately set them apart from the original Byakuya, becoming core traits of their character that remain evident throughout their time at Hope's Peak and during the Killing School Trip. They impersonate Ryota so that the real one can focus on pursuing his passion for making anime. They further continue to check up on him and care for his well-being even a year later, risking exposure to their secret as an Imposter when they bring Mikan to help care for him as his health deteriorates. As part of their Byakuya impersonation, they act arrogant, rude, and somewhat bad-tempered, but they're also reliable and feel responsible for others' safety. They indiscriminately care for their classmates, all of whom they consider "weak" and "inferior", believing they need to be guided. For example, they express no concern over whether Hajime remembers his talent—as long as he follows their lead, he still "will know peace" and that "everything will turn out fine." Even Fuyuhiko, who refuses to cooperate and threatens to kill others, is told he remains under their protection. They also show only mild irritation and never genuine dislike toward the more chaotic personalities among their classmates. Even Nagito, whom they discover was planning to commit a murder, is protected by them from being killed by Teruteru.

Another core trait of the Ultimate Imposter is their pride in their heavy build, which appears to be intentional, as they've stated they sculpted their physique that way on purpose and become upset when someone suggests they should lose weight. They also have a strong liking for food and are shown to be passionate and knowledgeable about topics related to eating, such as body fat percentages, the energy content of specific foods, nutritional values, different types of meats, and fast food restaurants. They explained that, since virtually all fast food restaurants serve the same kind of food, it gives them a sense of security to keep being around something familiar. They also boast that they can eat more than Akane Owari, the Ultimate Gymnast and fellow foodie, claiming it's due to having "overcome the hardships of the past"—hinting it to be their past outside of their Byakuya disguise. Although their original counterpart isn't as enthusiastic about food, the Imposter conveys this interest by often acting condescending toward skinny people and taking offense when someone eats in a cluttered, vulgar manner, piling food without any sense of theme or principle.

There are two instances where the Ultimate Imposter's true personality is shown while outside of their disguise. One occurs during a game reset sequence at the final trial of the Killing School Trip, where they speak briefly in a more polite manner than when in their disguise. In the original Japanese, they refer to themselves using the more polite pronoun "boku" (僕), instead of Byakuya's casual "ore" (俺). The other instance occurs when they reveal their face for the first time at Hope's Peak, shortly before The Tragedy. They display a collected and serious personality, determined to save their friends, which aligns with their naturally caring nature seen during the Killing School Trip. Despite gaining a better sense of self after the Final Killing Game concludes, they still prefer to remain in disguises (albeit only physically).

The Ultimate Imposter has no name, permanent address, birth certificate, or anything that could link them with their true identity even their age and sex. Their non-existent identity, however, allows them to exist as anyone by taking other people's data so they could impersonate them flawlessly. This is showcased in their impersonation of Byakuya, as they are able to accurately recount the history of Byakuya Togami and his family's special hereditary system. Moreover, they can perfectly impersonate the person in question's voice, personality, and talent, such as mimicking Byakuya's arrogance and leadership skills, as well as the ability to wield a katana when impersonating Kyosuke. Their imitation ability seems to have no limits based on gender. Although only showcasing their ability to impersonate men, creator Kodaka suggests that the Imposter has the potential to impersonate women, such as Celestia and Aoi.

According to Monokuma, their heavy physique does not affect their ability to fool others. At the beginning of the Killing School Trip, Nagito, who retains knowledge of his classmates' achievements as Ultimates, seemingly cannot differentiate the Ultimate Imposter from the real Byakuya, treating them as the same individual. While attending Hope's Peak, all members of Class 77-B, including Chisa, do not recognize the real Ryota's true appearance. When the real Ryota accidentally meets Chisa, she wonders how he could have lost so much weight in such a short time. It is also thanks to their impersonation of Koichi that they are able to help scout members of Class 77-B, which leads to their talent being recognized by the real Koichi himself, and consequently, they are enrolled in the same class.

Enhanced Agility - The Ultimate Imposter was designed by the creators to be an agile and nimble individual despite their heavy build. This is showcased during the Killing School Trip, where they move faster than anyone in the group. They are also able to effortlessly dodge all attacks from the Future Foundation during their tenure as a Remnant of Despair.