Hiyoko Saionji

Hiyoko's cute appearance, voice, and initial way of talking to strangers give the impression that she is innocent and childlike. In the original Japanese, Hiyoko refers to her classmates using childish honorifics like "onee" (おね, big sis) and "onii" (おにい, big bro), which enhances her childlike persona, though she pointedly excludes certain individuals—such as Mikan and Fuyuhiko—and omits it for those she has lost respect for, like Teruteru and Peko in the Killing School Trip. That first impression falters the moment she opens her mouth, as shown in her introduction to Hajime, where Hiyoko is revealed to be cruel, malicious, foul-mouthed and brutally honest. An early example is her tendency to torture small animals, like squishing ants because they make a satisfying popping noise when done correctly, and calling Hajime a wuss for refusing to join her. Later, at the beach, she goes around trying to step on and trample crabs, laughing as if it were just child's play, showing an alarming fascination with it. She also stomps on and tears out flowers for her own amusement, explaining that she likes to destroy pretty things.

The extent of her cruelty also extends to people, though it is rarely physical presumably due to her diminutive stature. In exchange, she often makes violent yet childish threats to others if they test her patience, such as threatening to bop them on the head with all her might or fantasizing about people capable of physical harm she can easily manipulate, like Akane, to do the bopping on her behalf. This explains her taking pride in her growth spurt, playfully stating that she now can "bend Mikan's bones in any direction." For the likes of Hiyoko, however, her harsh words and mean-spirited behavior are enough to gain her notoriety and a reputation for cruelty. She constantly judges others, sometimes uses swearing, and patronizes them with highly insulting yet unique nicknames, such as "Mr. Ham Hands" for the Ultimate Imposter, "nasty, toilet-clogging bitch" and "four-eyed troll" for Peko, "tiny boy" for Fuyuhiko, and the most infamous "pig barf," "pig-faced troll", and "filthy pig" among others for Mikan.

As shown by the many degrading nicknames Hiyoko gave to Mikan, she quickly latched onto her as her favorite bullying target, both during their time as classmates and in the Killing School Trip, due to Mikan's timid nature and lack of will to fight back.[4][46] She would often insult Mikan just by existing. She would worsen such insults when Mikan irritated her in the slightest, to which Mikan would only respond with constant apologizing for being a "pig barf."[31][34][35] Their bully-victim dynamic is even perfectly replicated in the Twilight Syndrome Murder Case, with Hajime managing to deduce who is who based on the real-life dynamic between Hiyoko and Mikan—where Girl B is rude and mean to the helpless Girl A.[34] Hiyoko suspects many parts of Mikan's behavior (such as her clumsiness and poses) are an act, causing her to strongly dislike her.

Another type of person she loves to tease is someone who shows a strong upset reaction, like Kazuichi. She doesn't hesitate to insult him when given the chance, calling him all sorts of names like "useless," "boring," "unpopular," and so on. She believes these insults are justified by his cowardice at the early stage of the killing game and how he behaves around Sonia, which only doubles her annoyance as she views him as a pathetic virgin. It was revealed that Hiyoko frequently picks on Kazuichi largely due to her dislike and jealousy toward Sonia, stemming from how much attention Sonia receives from the other students. This is why taking jabs at gullible people like Akane—while fun and something she often does throughout the killing game—is ultimately less rewarding for her.

Hiyoko's mean and cruel behavior could be explained by what she has been through in her childhood as the heiress to the famous Saionji Clan. With her overbearing grandmother, and jealous people playing lots of cruel and even potentially life-threatening tricks and threats on her, she became very distrustful of other people and seemingly developed her mean personality as a defense mechanism. The only person she trusted and felt safe with was her father, who was different due to being related to the family only through marriage. As such, in Island Mode and her Free Time Events, she grows fond and protective of Hajime as a big brother figure, because he reminds her of her father, who is very dear to her. Another side effect of her past is her hatred of being deceived. She felt annoyed and openly admitted to disliking being tricked, as shown during Mahiru's murder investigation when Nagito spread a made-up lie about an emergency meeting[34], and again when he contracted the Despair Disease.

Hiyoko, who grew up constantly being envied and targeted by others, eventually developed a sense of superiority, along with a firm belief that the concept of "friends" is nothing more than "a bunch of weaklings who decide to get along and play nice." As such, she stated that she never needed any friends or any close contacts. This mindset uniquely makes her a level-headed person in the killing game, as while many hated the prospect of doubting friends, she was the first to accept the reality that someone in the group had murdered the Ultimate Imposter and urged everyone to investigate if they truly wanted to survive. Her beliefs also caused her to snap at Akane, the others, and possibly even herself after witnessing Nekomaru sacrifice himself to protect Akane. She claimed that relying on teamwork, cooperation, and friendship was just a way to fool themselves. In her view, stupid people like Akane, who caused Nekomaru to act on his "weird feelings of friendship," would only lead to everyone getting killed one by one — reinforcing her refusal to rely on anyone. She was also selective in choosing who to sympathize with. For instance, she felt bad about the Ultimate Imposter's death, acknowledging their important role as the group's de facto leader who didn't seem to mind the insulting nickname "Mr. Ham Hands" she had given them. She also didn't place full blame for Mahiru's death on Peko, instead directing all her anger and resentment toward Fuyuhiko, whom she called out as the true cause of both girls' deaths. After Teruteru was executed for his crime, she was also the only one who did not sympathise with his death, saying that he deserved it.

As someone who believes she's a "perfect human", Hiyoko becomes very manipulative and often coerces others into doing her bidding—Akane being a frequent target. Even Kazuichi didn't defy her order to build a communication device after some students contracted the Despair Disease. During her Free Time Events, she also orders Hajime around and wants him to be her slave. If she doesn't get what she wants or if other people actually talk back to her, she tends to cry crocodile tears loudly like a child. Though her tears are sometimes genuine, her dishonesty makes it difficult to discern when she is experiencing sincere distress and when she is being emotionally manipulative, in a "boy who cried wolf" effect.

Raised by a traditionalist family, Hiyoko developed a genuine love for Japanese traditions and culture. However, it also manifests as a form of superiority as she tends to act condescendingly or even openly insult other cultures. She considers many Japanese things "delicate, refined and high quality". She is especially fond of Japanese cuisine and candies, claiming that foreign ones are too sugary and gross and the people eating them are gross as well. She has described some other countries as worthless and compared their people to stupid animals, thinking that Japan doesn't need to import from them. As a rarer good trait, however, Hiyoko is stated to be willing to protect old traditions in danger of disappearing and she thinks people should take good care of the things close to them. She has also stated that she knows her thinking is old-fashioned, but she doesn't intend to disagree with new directions, just to protect old ones that need to be protected. Despite her traditionalist upbringing she has a lot more unconventional interests, such as heavy metal (being the only person in the class who liked Ibuki's performance) and horror movies.

Despite her claim to superiority, Hiyoko is very clumsy at anything other than dancing, which she admits, possibly due to her spoiled upbringing. An example is that she cannot tie her own kimono sash, preventing her from showering. As a result, she began to smell bad and felt attacked and agitated when everyone confronted her about it, eventually bursting into tears. She then became attached and vulnerable to Mahiru so quickly when she offered to tie her sash and acted very affectionately towards her, often happily wanting to hold her hand or hug her, and even giving her a kiss. This contradicts her claim of not needing friends, though Hiyoko has stated that she likes Mahiru because she is normal and not as weird as the other students.

Her relationship with Mahiru in the Killing School Trip mirrors their relationship while attending Hope's Peak Academy. She quickly bonds with Mahiru, whereas it takes Hiyoko some time to open up and warm up to the other students. Throughout Danganronpa 3 - Despair Arc, it is shown that she gradually tolerates her classmates and even enjoys their company by teasing or pulling pranks on them. The most notable example is her relationship with Mikan. Despite still being a bully to her, Hiyoko grows fond of her during their high school years together, although she prefers to keep this part of her hidden. When Mikan was missing and everyone thought that the person who entered the room was Mikan (though it was quickly revealed to be Nagito), Hiyoko cheerfully greeted him with "hey, girl" and appeared very relieved when she thought that Mikan was confirmed to be safe. She even reluctantly admits that Mikan's talent is useful when medical attention is needed. She also properly thanked her, while shy, after Mikan saved her from the attack of the Super High School Level Nailist. Kodaka has indicated that their illusion counterparts' relationship in Danganronpa 2.5 may have some reflection on their real relationship, showing that Hiyoko has grown protective of Mikan and doesn't want anyone else to bully her.

However, her growth and acceptance of others is relatively slower with the tension of the killing game looming over her, compared to her time at Hope's Peak Academy, as she resorts to her mean, superior persona to protect herself in such a life-threatening situation. Unlike Fuyuhiko—who, after losing Peko, expressed genuine remorse and actively worked to change—Hajime noticed that Hiyoko, still grieving Mahiru's death, remained just as mean as ever and struggled to forgive him. However, she did create a memorial for Mahiru, and while she never explicitly admitted it, she began to change little by little—attending Fuyuhiko's welcome-back party and while still not forgiving him, eventually showing a willingness to cooperate with him until they could leave the island. With Mikan, the "best" development between the two is that whenever Mikan praises Hiyoko for trying to change, Hiyoko insults her and calls her names—yet does so with teary eyes and a blush.

Hiyoko enrolled in Hope's Peak Academy as the Ultimate Traditional Dancer. She is the heiress of the Saionji Clan, which is famous for its traditional Japanese dancing. As a promising young member of the world of traditional Japanese dance, she performs often, even abroad, despite being so young. She is popular among young and men audiences, which is rare in the Japanese dance industry. Crowds of audience members are drawn to her un-high school student-like appearance and cute voice. However, she stated that most people who aren't used to watching traditional dance performances often fall asleep easily.