Sylph appears as a tiny, young female with a pair of insect-like wings and pointed ears. She has green hair, green eyes, and fair skin. Charmy claims she has a large forehead.
She wears a short, pale-green sleeveless dress and no footwear.
Sylph appears to be playful and free, like the wind itself. She is also shown to be quite energetic and lively. As his familiar, she's very protective and obsessive to Yuno, and would turn hostile to any girls approaching him.
While exploring the dungeon's treasure room, Yuno is drawn to a scroll containing mysterious writing. As he reads the words, his grimoire and the scroll begin glowing, and the writing disappears in a flash of light.
Desperate to save Asta from Mars, Yuno breaks free from his restraints and strains to find a spell to help him. Time seems to stop and Sylph appears next to Yuno. She yawns and then blows a kiss toward Laevateinn, shattering the sword and blasting Mars into a wall. Afterwards, Yuno notes the disappearance of Sylph and the appearance of the scroll's words in his grimoire.
Upon returning to the capital, Yuno shows his grimoire to Julius Novachrono, who can read a little of Sylph's entry. He asks for a demonstration but Yuno admits that he has not been able to summon her again. Disappointed but intrigued, Julius tells Yuno to treat her well.
During the invasion, Sylph alerts Yuno of Valtos' Blackout, saving him from being scattered with the other Magic Knights. Catherine attacks Yuno and removes most of his senses with Joyful Destructive Ash, but determined to keep up with Asta, Yuno summons Sylph and uses Sylph's Breath. The spell blasts Catherine into a tower, and Yuno realizes that Sylph has been showing him where the mana is. She hovers near Yuno as he chases after Catherine and saves Charmy Pappitson's food.
Sylph joins Yuno and other Golden Dawns when they arrive in Kiten to defend it from the invasion by the Diamond Kingdom. After Yuno takes out Broccos, Sylph complains that Yuno did not use her power, does not smile enough, and ignores her too often. When Ragus confronts him, Yuno asks for Slyph's help, and she increases the power and speed of his Gale White Bow's arrows, which overpower Ragus' arrows and pierce the general's defenses. Broccos and Ragus then argue over who gets to fight Yuno, but Sylph declares that the boy is hers.
After defeating Ragus, Yuno lands and greets Asta with a smile, which shocks Sylph. She becomes flustered as Yuno talks with Asta and she hears about their past together. Charmy then interrupts and offers Yuno some food, which frustrates Sylph. When Yuno apologizes for pushing Charmy, Sylph is shocked and accuses Charmy of using Charm Magic on Yuno, and the two women bicker while Yuno and Asta tell them to stop.
After the Black Bulls defeat Yagos, Sylph is shocked to see Yuno smiling while saving Asta. As the two teams bid farewell, Charmy asks for Yuno's contact information, and Sylph wards her off by scattering scales in her eyes. The spirit then returns to Yuno's shoulder and sticks her tongue out at Charmy, whom Finral Roulacase drags through his portal.
Afterwards, Langris Vaude talks to Yuno and asks him about his rivalry with Asta. When Yuno replies that they are competing for the seat of Magic Emperor, Langris ridicules the idea, and Sylph warns the vice-captain about making fun of Yuno. She is quiet after Yuno declares that he must become captain first.
At the Star Awards Festival, Sylph accompanies Yuno onstage when he is recognized for contributing the most stars to the Golden Dawn. After Asta joins Yuno onstage to represent Black Bull squad, Sekke Bronzazza calls out the pair for being commoners, so Yuno has Sylph release their full combined power, which shocks the crowd. Yuno then fires an arrow at Asta, who cuts it with his Demon-Slayer Sword, creating a gust of wind that surprises the spectators.
Sylph accompanies Yuno when Mereoleona Vermillion takes him and others to Ultime-Volcano Mountain Trail for training. Sylph hops out of Yuno's hood because of the heat, and when he protects himself with his mana and creates a small whirlwind of cool air, she flies with him to the summit.
A week later, she accompanies Yuno to the Royal Knights Selection Exam and claims that she was promised a date, which he denies. Later, she watches the matches while perched on Yuno's shoulder. She is surprised when Charmy appears and sidles up next to Yuno. Later Sylph complains that Noelle Silva is too loud after the girl starts yelling at Yuno, but turns her attention to warding off Charmy again.
In the final match of the tournament, Sylph and Yuno take on Rill Boismortier, who uses his Painting Magic to seal Sylph's attacks, so Yuno merges with Sylph using Spirit Dive, which enables him to equal Rill and to win the match.
Several days later, Sylph accompanies Yuno on the Royal Knights' mission to infiltrate the Eye of the Midnight Sun base. As Yuno's team make their way into the dungeon, Yuno begins hearing something and Sylph asks him about it. When they reach the central room, they find Licht floating in a giant sphere of mana, and Sylph is worried about the feel of the mana.
After Patolli places the last magic stone within the stone monument, Yuno is possessed by an elf spirit. Sylph and Yuno watch silently as Hamon Caseus and Klaus Lunettes fight and defeat Mimosa Vermillion.
- Wind Magic: As the spirit of wind, Sylph uses this form of magic to generate and manipulate wind.
- Immense Magic Power: As a spirit, Sylph possesses a vast amount of magic power.
- Yuno vs. Catherine: Win
- Yuno vs. Ragus: Win
- Asta and Yuno vs. Two Elves: Win
- Asta and Yuno vs. Licht: Loss
- Hidden Treasures: the Sword and the Wind
- Invasion of Kiten
- Royal Knights Selection Exam
- Attacking the Eye of the Midnight Sun Base
Sylph falls in love with Yuno and she's willing to protect him everywhere at all costs.
- Sylph's favorite thing is to mock others, except Yuno.
- A sylph is a mythological spirit attributed to air by Paracelsus.
- Her nickname and design are references to the fairy Tinker Bell from J. M. Barrie's play Peter Pan.
- Sylph ranked 58th in the second popularity poll.