Fuyumi Yanagi

Yanagi Fuyumi (柳冬実) is the human high-school-aged girl from Japan who becomes lost in the Demon World after traveling through the  mysterious Black Curtain. She becomes a ghost after being eaten by a carnivorous plant. The triangle headband she dons on her head is a symbol of this. After she becomes a ghost, Staz vows to bring her back to life.

Appearance
Fuyumi is a 16-18 year old girl with shoulder-length black hair and purplish blue eyes. She has pale skin and a big bust. She was once a human but she is now a ghost. After her death, she always dons a triangle-shaped headband which is a common symbol to denote that a being is a ghost in Japanese culture.

Personality
Personality-wise, Yanagi is shown to be a kind, sensitive, and supportive person though she can also be naive & shy. She often finds herself astounded and sometimes annoyed by Staz's lack of common sense, yet she eventually has unquestionable faith in him, although she isn't afraid to stand up for what she likes or what she believes in. She tends to act as a foil to Staz's more outrageous personality. She wishes to be resurrected as a human, and strives to help Staz achieve that goal. It is also noted that she is excellent in using proverbs to describe the odd situations she finds herself in with Staz.

Her name means "weeping willow".

Plot
Fuyumi first stumbles into the demon world after being transported through a magical Black Curtain. However, it is still unknown how and why she is there, because it is also hinted that she may play a pivotal role in Braz's plot to overthrow the current Demon King, Father Wolf. After getting lost in the demon world, she is brought to the Territory Boss, Staz Charlie Blood, the main protagonist of the series, who wanted to meet her.

Because she is from Japan, and he is an otaku, Staz is even more interested in her, often asking about anime and manga from the human world. After Staz leaves to fight a challenger, she is eaten by a carnivorous plant, and turns into a ghost as a result. When Staz learns of this, he vows to protect her and bring her back to life. In order to do this, however, He must meet many people and go through many challenges.

It is later revealed she is the sister of Hydra Bell and the daughter of Neyn.

Techniques
Franken Stein theorizes that due to her nature as a ghost, she will become a very powerful hybrid because she has the ability to absorb and utilize multiple types of magic from other demons, though it requires her to have a source to 'feed' off of, such as Staz's blood. Because of this, he believes that Fuyumi will eventually become powerful enough to rival Staz.

Weakness

 * Fuyumi's ghost body is, as Staz explained, an inefficient vessel to hold a tremendous power from Staz' himself, thus resulting for her body to become tiring and slowly disappears starting from her limbs. However, if she doesn't acquire Staz' blood to replenish her "mana", she won't be able to live in the demon world and her existence might completely be erased.

Known Family
Father: Yanagi (unknown first name)

Mother: Neyn

Sister (no blood relationship) : Hydra Bell

Brother (half) : Hydra Knell