Kei

Presentation

Kei Yonagi is the main heroine of the manga Act-Age, a drama series centered on the world of theater and cinema. Aged 16, she is a sophomore at Suginami Kita High School, but her life is far from ordinary. Motherless and abandoned by her father, she is raising her two younger siblings, Rei and Rui, on her own in precarious conditions. Despite these hardships, Kei possesses an extraordinary talent for acting, in particular the actor's method, a technique in which she draws on her own traumas to embody roles with disconcerting intensity.

Her journey began when she was spotted by renowned director Sumiji Kuroyama, who saw in her the potential to become a legendary actress. Unlike traditional actresses, Kei doesn't play a character-she becomes the character, sometimes to the point of losing control of herself. This radical, yet ingenious, approach has earned her both admiration and fear in the entertainment world.

Appearance

Kei Yonagi is distinguished by a slender figure and a presence that is both fragile and intense. At 168 cm, she is taller than the average girl of her age, which reinforces her aura on stage. Her black hair, cut to a mid-length, ends in slightly upturned tips, and a rebellious lock (ahoge) gives her an air both serious and childlike.

Her eyes, deep black with violet or red highlights, are her most expressive tool. They can go from a blank stare to all-consuming emotion in an instant, reflecting her ability to slip into a trance-like state when she's playing. Her face, often neutral in everyday life, becomes extremely mobile when she's playing a role.

Dressed in a sober school uniform (first white and blue with a red ribbon, then black and red), she doesn't seem particularly concerned with her appearance outside of filming. And yet, when she's preparing for a role, she completely transforms herself, whether as an innocent young girl, an androgynous boy, or a demonic woman.

Personality

Kei Yonagi is a living paradox. Outwardly, she seems calm, almost aloof, with a tendency to remain silent in normal conversations. But when it comes to acting, she explodes with an almost terrifying energy. Colleagues describe her as “scary” or “obsessed”, as she knows no half measures when immersed in a character.

Yet behind this intensity lies a deeply empathetic and vulnerable young woman. She uses cinema as an escape from her painful reality, but this escape sometimes becomes dangerous. She finds it hard to separate fiction from reality, which leads her to unconsciously adopt the traits of her characters even off the set.

Despite her dark side, Kei has an endearingly awkward side. She's naïve on many subjects, marvels at simple things, and can have eccentric reactions-such as screaming with joy at the discovery of a new film or panicking in the face of mundane social situations.

Roles (and Story)

Young Girl / Stew's for Father's Day

Kei Yonagi lives a difficult life, juggling classes, odd jobs and looking after her siblings. One day, she attempts an audition for the Stars agency, but her performance is so powerful-and so dangerous-that she fails. However, director Sumiji Kuroyama, present in the audience, saw in her a rising star. He offered her her first opportunity: a commercial.

For this role, Kei has to express filial love - an emotion foreign to her, her father having abandoned the family. So she recalls the times when she used to cook for her siblings, transposing this sibling affection into fatherly love. The result is overwhelming, but after the shoot, she realizes that she can't even smile naturally for her family. This paradox marks the beginning of her journey: can she be a great actress without losing herself?

Original Character / Death Island

Kuroyama offers her a role in Death Island, a horror film produced by Stars. Kei is to work alongside Chiyoko Momoshiro, an established actress nicknamed “The Angel” for her pure, elegant acting. While Chiyoko embodies technical perfection, Kei plunges into her character with instinctive savagery.

During a group audition scene, Kei loses control and improvises a violent attack, shocking everyone. Some find her brilliant, others dangerous. During the shoot, she has to face a real storm for a key scene, proving her total commitment. This arc shows her first steps in the professional world, where she learns that raw talent isn't enough-you also have to know how to work as part of a team.

Campanella / Night of the Galactic Railroad (銀河鉄道の夜)

Kei is chosen to play Campanella, a young dead boy, in a stage adaptation of Night of the Galactic Railroad. The director, Yujiro Iwao, is a stern and dying man, who demands an absolute performance from her. For the first time, Kei has to play a male character, which pushes her to her limits.

She spends weeks studying the boys' gestures, modifying her voice, and above all, drawing on the tragedy of Iwao-who, like Campanella, knows he's going to die. The premiere is a triumph, but Iwao dies shortly afterwards, leaving Kei devastated. Yet this experience transforms her: she is no longer just an emotional actress, but a performer capable of conveying universal melancholy.

Iron Princess Fan / Journey to the West (西游记)

The last major arc of the manga sees Kei confronted with her greatest challenge: a role in Journey to the West. To play the Princess, she must express pure rage-an emotion she has always repressed. Then producer Hanako Yamanoue reveals a shocking secret: she had an affair with Kei's father, and it was because of her that he left his family.

This betrayal becomes the fuel for her performance. On stage, Kei explodes in a terrifying, almost uncontrollable performance. Yet, on the verge of chaos, she finds a balance and delivers a masterful performance. This arc marks her passage into adulthood, where she learns to tame her demons rather than let them consume her.

Post-Arc Developments

The manga was abruptly canceled in August 2020 due to the writer’s arrest, leaving the Taiga Drama Arc (Kei’s rise to stardom) unresolved. Despite this, Kei’s legacy endures as a symbol of transformative acting.

Relationships

Kei Yonagi’s journey in Act-Age is deeply shaped by her interactions with key figures in the acting world—mentors who challenge her, rivals who push her to her limits, and allies who keep her grounded. Here’s a breakdown of her most important relationships:

Sumiji Kuroyama

Kei’s relationship with Sumiji Kuroyama is the cornerstone of her career. A legendary director known for his ruthless perfectionism, Kuroyama sees something terrifyingly brilliant in Kei from their first meeting. Unlike traditional mentors, he doesn’t coddle her—he weaponizes her instability, pushing her into roles that exploit her trauma to create unforgettable performances.

• Dynamic: Less like teacher-student and more like a mad scientist and his experiment.
• Conflict: Their bond frays during Journey to the West/Monkey King Arc when he directs the rival team, forcing Kei to prove she doesn’t need his guidance to shine.

Yuki Hiiragi

She serves as the studio's mother figure, tempering Kuroyama's excesses. Yuki supports Kei behind the scenes, especially during the stressful shoot.

Chiyoko Momoshiro

Chiyoko Momoshiro, nicknamed "The Angel" for her ethereal acting style, is Kei’s polar opposite. Where Kei is raw and destructive, Chiyoko is precise and luminous. Their rivalry begins on Death Island, where Chiyoko is initially dismissive of Kei’s "messy" method—until she witnesses its power firsthand.

• Dynamic: A battle between instinct (Kei) and technique (Chiyoko), but with mutual respect.
• Conflict: By Monkey King Arc, they push each other to new heights, with Chiyoko acting as Kei’s rival.

Arisa Hoshi

She fears that Kei's game will destroy her mentally, reflecting her own past traumas. Her initial rejection of Kei adds narrative tension.

Akira Hoshi

Son of Stars' CEO, he steps in to save Kei from disqualification. He is a brotherly figure, although their interactions remain professional.

Araya Myojin

Method actor like Kei, but experienced. He teaches her to channel her emotions to avoid losing herself in her roles. Their relationship is likened to that of an older brother.

Rei and Rui Yonagi

Kei assumes the role of parent after the death of their mother and the departure of their father. Although her siblings find her “scary” because of her strange behavior (like her forced smile), they support her acting career. Rei admires her ability to immerse herself in films to forget their financial difficulties.

• Dynamic: Protective but distant. Kei hides her emotions to reassure them, but her immersion in acting creates an emotional barrier.

Father (Unnamed)

He has abandoned the family but sends money, which Kei refuses out of pride.

Arata Yoshioka and Hina Asahi

School friends who help Kei integrate socially. Hina, initially cynical, is touched by Kei's sincerity.

• Dynamic: A balance between normality and art. Kei discovers ordinary life through them, while passing on her passion for art.

Trivia

• Favorite Films: Roman Holiday, Casablanca, Gone with the Wind.
• Theme: Her name "Kei" (景) means "scenery"; "Yonagi" (夜凪) means "night calm"