Yuka Hagiwara (萩原 由佳) is a first-year student at Kuromata High School and Ruri Aoki's oldest friend — her commute buddy, her lunch partner, and the first person Ruri thought of when she woke up with horns. She is 15 years old, 152 cm tall, blood type A, and her birthday is October 21st.
She is highly sociable, makes many friends, and is — by the author's description — "pretty indifferent" about most of them. This selective indifference is exactly what makes her the ideal person to be Ruri's best friend. Most people treat Ruri's draconic traits as a significant thing to be managed. Yuka treats them as mildly interesting information and then continues being Ruri's friend. She was the first person to touch the horns on the morning they appeared. She had a low-key reaction. This was what Ruri needed.
Her loyalty vow — "If you drop out of school, I'll follow you, Ruri" — is the most significant thing anyone says to Ruri across the series' social arc. Not because it resolved anything biologically, but because it removed the condition from the friendship. Whatever happens next, Yuka is there. That is the most stabilising thing a person facing draconic transformation could be told.
Yuka is a short teenage girl standing at 152 cm (an update from the Chapter 12 profile which listed 148 cm — the revised figure is the current canonical measurement). She has short, naturally light-coloured blonde hair and a pair of persistent cowlicks on the right side of her head that she is unable to flatten regardless of effort. The cowlicks appear in every chapter. They have not been resolved.
She is most frequently seen in the Kuromata High School uniform — the standard dark blazer or a knit vest during warmer months. Her casual wear is fashionable and comfortable: oversized jackets, light-coloured sweaters, practical outfits that read as put-together without being formal. The author noted she has "gotten cuter since the original one-shot" and was designed with the "ideal friend" aesthetic in mind — someone who looks approachable and ordinary in the best possible way.
Yuka is sociable, blunt, selectively loyal, and specifically not interested in treating Ruri's biological situation as a problem. The combination of these traits produces a friend who is simultaneously easy to be around and impossible to shake.
Indifference as a Virtue
The author describes her as "pretty indifferent" about most of her friends — even more so than Ruri. This is not unkindness. It is the absence of the conditional investment that makes other friendships fragile. She makes many friends and doesn't particularly mind most of them. Her deep bond with Ruri is the exception to the rule, which makes it the most solid thing in Ruri's social world: if Yuka's baseline is indifference and she still chose Ruri as her closest friend, then Ruri knows exactly what she is to Yuka without ambiguity.
The Nonchalance
She had a low-key reaction to the horns on the morning they appeared. She touched them. She used Ruri's phone to call Umi Aoki for information. She treated the fire-breathing incident as something to be checked on rather than afraid of. Ruri's electrostatic discharge, venom, frost — Yuka's response across all of these has been consistent: minor inconvenience, concern for Ruri's wellbeing, continued friendship. She does not walk on eggshells. She does not require Ruri to manage her reaction before managing her own situation.
Blunt Honesty
She tells Ruri that she is a "people pleaser," a "pushover," and "borderline obsessed with how others view her." These are accurate assessments delivered without cruelty. Yuka understands Ruri's psychology well enough to articulate it clearly to other people, which is the kind of knowledge that comes from years of close attention. She uses it to explain Ruri's behaviour to Maeda. She uses it to Ruri directly when it is useful. Neither delivery is unkind.
Fierce Loyalty
She stayed in the nurse's office for an entire afternoon after Ruri's venom-induced collapse despite having a lengthy commute home. Her reason: they are commute buddies. The loyalty is expressed through presence — she shows up, stays, and refuses to make it seem like a significant sacrifice when it is.
The Morning of the Horns — Chapter 1
Ruri's first thought upon waking with horns was that Yuka was probably already waiting at their meeting spot. She was right. On the bus, Yuka was the first peer to see the horns and touch them — with the specific low-key reaction that Ruri found more comforting than a dramatic response would have been. She used Ruri's phone to call Umi Aoki. She treated it as information management rather than a crisis.
The Return to School — Chapters 5–7
After Ruri's fire-breathing incident, Ruri spent a week at home too afraid to return to school. Yuka visited to check on her burn. When Ruri finally did go back, she went specifically because Yuka came to get her — the physical presence of her friend was the deciding factor, not institutional encouragement or her own courage working through the anxiety on its own. Yuka's visit was the intervention. "Yuka came to get me" is how Ruri describes the reason she returned.
The Nurse's Office — Chapter 19
Ruri manifested venom during a committee meeting and passed out. Yuka stayed in the nurse's office until Umi Aoki arrived — an entire afternoon, with a lengthy commute ahead of her afterward. Her explanation when asked why she stayed: "Because we're commute buddies, duh?" The logic was not elaborate. The loyalty behind it was complete.
The Loyalty Vow — Chapter 40
In a moment of genuine vulnerability, Ruri expressed fear that she was becoming less human and might be forced to leave school. Yuka's response: "If you drop out of school, I'll follow you, Ruri." The vow is unconditional and specifically removes the school environment as a requirement of their friendship. Whatever Ruri's biology demands, Yuka is there. The statement gave Ruri the emotional basis to choose to stay rather than withdraw — not because it fixed anything biological, but because it made the stakes of leaving lower.
The Spurt and the Empty Desk — Chapters 43–47
As Ruri's biological Spurt intensified — glowing eyes, constant exhaustion — Yuka was among the first to notice. When Ruri's leave of absence took her to Mount Ontake, Yuka was shown in class staring at Ruri's empty desk. It is the series' quietest depiction of what Ruri's absence means to the person whose daily routine is built around her presence.
Ruri Aoki — Best Friend and Commute Buddy
Yuka and Ruri have been close since middle school — where, notably, Ruri reached out to Yuka first, not the other way around. The reserved loner extended the first connection. Yuka accepted it and has not wavered since. Their friendship is defined by daily proximity (commute buddies, lunch partners, study group), Yuka's consistent refusal to treat Ruri's biology as a problem, and the specific bluntness of someone who knows another person well enough to tell them true things that are hard to hear. Ruri's return to school after the fire incident, her decision to stay enrolled when she feared she might have to leave — both were shaped by what Yuka said and did at exactly the right moment.
Umi Aoki — Trusted Extension of the Household
Yuka is a fixture in the Aoki household. Umi coordinates with her by phone and Line to check on Ruri's wellbeing, to confirm the classroom survived draconic incidents, and explicitly to leave Ruri in her "capable hands." Their relationship is warm and practically functional — Umi trusts Yuka as the first-response person for Ruri at school, and Yuka accepts that role without it feeling like a burden.
Akari Maeda — Recognised Champion
Yuka initially viewed Maeda with some suspicion due to her bluntness, but eventually acknowledged her as Ruri's "champion in shining armor" for her proactive support. The evolution from wariness to recognition is consistent with how Yuka operates: she evaluates people on their actual impact on Ruri rather than on surface-level assessments.
Airi Kashiro — Study Group and Dragon Research
Yuka participates in Dragon Research sessions and study groups with Airi and Ruri, and coordinates remote study access when Ruri is absent. Their friendship is warm and social without having the specific weight of the Ruri-Yuka bond — a good friendship rather than a primary one.
Kana Miyashita — Social Circle
Miyashita stayed with Yuka in the nurse's office to watch over Ruri after the venom incident. She is part of the broader social and study group but not among Yuka's closest connections.
- Yuka's birthday is October 21st, her blood type is A, and she is 152 cm tall. The height appears in two versions in the source material: 148 cm in the Chapter 12 profile and 152 cm in a revised profile. The 152 cm figure is the current canonical measurement.
- She has persistent cowlicks on the right side of her head that she cannot fix regardless of effort. They appear in every chapter. The author appears to have decided they are a permanent fixture.
- Author Masaoki Shindo described her as the "ideal friend" and noted she has "gotten cuter since the original one-shot." The design intention was someone who embodies the specific quality of a friend who makes things easier to bear by treating them as ordinary.
- She has a lengthy commute to Kuromata High — longer than Ruri's. She stayed in the nurse's office all afternoon anyway after Ruri's venom collapse. The commute detail exists in the series specifically to make the nurse's office stay more significant: it was not convenient, and she did it regardless.
- The vending machine on the way to school is always sold out of Dr. Pepper. This frustrates her regularly. It is the most mundane and human detail in her profile and the series includes it deliberately — she is, in every possible way, an ordinary person whose ordinary concerns are part of what makes her the right person to keep Ruri grounded.
- Ruri reached out to Yuka first in middle school — not the other way around. The "reserved loner" making the first connection is one of the series' quieter character details, because it means the friendship is something Ruri actively chose before she had any reason to need it. Yuka is not someone who found Ruri. Ruri found Yuka.
- The loyalty vow in Chapter 40 — "If you drop out of school, I'll follow you" — is delivered as a simple statement rather than a dramatic declaration. Its power is entirely in its unconditional framing: no qualifications, no conditions, no suggestion that the outcome of Ruri's biology changes anything. The simplicity is what makes it the most important thing anyone says to Ruri in the social arc of the series.