Fuyumi Yanagi is a teenage girl, estimated to be between 16 and 18 years old. She has shoulder-length black hair and large, dark blue eyes that reflect her gentle and soft-spoken nature.

At the beginning of the series, Fuyumi wears a typical Japanese high school uniform. However, throughout the manga, she is often seen in various other outfits, depending on the situation or environment.

After her untimely death and transformation into a ghost, a key visual marker of her new form is the triangular headband she wears on her forehead. This is a traditional symbol in Japanese culture, often used to indicate that someone is a spirit or ghost.

Fuyumi Yanagi is a kind-hearted, gentle, and supportive girl who often acts as the emotional anchor among those around her. She is characterized by her soft-spoken nature, sensitivity, and unwavering patience. Despite her calm demeanor, Fuyumi can be quite naïve and shy, especially when caught in the eccentric chaos caused by the supernatural beings she interacts with.

She frequently finds herself bewildered or mildly annoyed by Staz Charlie Blood’s reckless and unpredictable behavior, yet she grows to place deep trust in him. Her faith in Staz becomes unshakable, though she is not afraid to speak up when it comes to her own values or beliefs, revealing a quiet inner strength.

As a character, Fuyumi often serves as a foil to Staz’s bold and over-the-top personality, grounding him with her more rational and sincere outlook. Her ultimate desire is to be resurrected and return to life as a human, and she remains committed to helping Staz fulfill that goal.

Notably, Fuyumi has a talent for using Japanese proverbs to describe the bizarre and often comedic situations she finds herself in, adding a unique charm and touch of wit to her character.

Fuyumi Yanagi first enters the Demon World after unknowingly walking through a mysterious portal known as the Black Curtain, located in her own room. Upon arrival, she is taken to the local Territory Boss, Staz Charlie Blood, a powerful vampire and the main protagonist of the series.

Being a human from Japan, Fuyumi immediately captures Staz’s attention, not only because she is a rare human in the Demon World, but also because Staz is a passionate otaku. Fascinated by Japanese culture, he eagerly questions her about anime and manga from the human world.

However, tragedy strikes shortly after their meeting. While Staz leaves to deal with a challenger, Fuyumi is devoured by a carnivorous plant, and her body is destroyed. She returns as a ghost, symbolized by the traditional triangular headband on her forehead. Devastated by what happened, Staz vows to protect her and bring her back to life, setting the foundation for the series’ central quest.

To fulfill his promise, Staz must overcome numerous obstacles and forge alliances with powerful beings across the Demon and Magic Worlds. This journey also leads to the gradual uncovering of Fuyumi’s mysterious origins.

Eventually, it is revealed that Fuyumi is the daughter of Neyn, a key figure in the Magic World, and the sister of Hydra Bell and Hydra Knell. This connection to powerful bloodlines adds greater weight to her existence and the mission to restore her humanity.

Due to her nature as a ghost, Fuyumi Yanagi possesses a unique magical potential. According to Franken Stein, a specialist in magical science, Fuyumi has the latent ability to become a powerful hybrid being. Unlike most entities, she can absorb and utilize multiple types of magic from other demons.

However, this ability is not self-sustaining. In order to activate and maintain these powers, Fuyumi must rely on an external magical source, most commonly Staz Charlie Blood’s blood. His powerful vampiric energy acts as a catalyst, enabling her to temporarily harness various magical attributes.

Stein speculates that, given time and development, Fuyumi could grow strong enough to rival even Staz, who is one of the most powerful demons in the series. This potential makes her a key figure in the evolving supernatural conflict, despite her currently passive combat role.

As a ghost, Fuyumi Yanagi’s existence is inherently unstable and dependent on external sources of magical energy. According to Staz Charlie Blood, her ghost body is an inefficient vessel for containing the immense magical power that she occasionally channels, particularly his own vampiric energy. This mismatch causes physical strain, leading parts of her ghostly form, such as her limbs, to fade or vanish temporarily when her energy is depleted.

Fuyumi must regularly replenish her mana to maintain her presence in the Demon World. The most effective and immediate method is by receiving Staz’s blood, which serves as a potent magical source. Without this replenishment, her ghost form begins to deteriorate, and she faces the risk of complete erasure, ceasing to exist entirely.

This fragile condition makes her extremely vulnerable and reliant on Staz, while also highlighting the urgency of his mission to restore her to life.

The given name Fuyumi (冬実) is composed of fuyu (冬), meaning “winter,” and mi (実), meaning “fruit,” “truth,” or “good result.” Her surname Yanagi (柳) translates to “willow,” a tree often symbolizing grace, resilience, and melancholy in Japanese culture.