Mist Hashira Seina Yūrei 幽霊 清名

Demonslayer: Kimitsu No Yaiba

Name: Seina Yūrei 

Title: Mist Hashira

Breathing Style: Breath of Mist, Kasumi no Kokyu

Backstory:

Seina is a timid mountain girl (around 11 years old ) who lives in a village often blinded by thick fog and mist most of its days and nights. At an early age, she lost her family to demons, but luck would have it, that day, a traveling Demon Slayer happened to see her. These mist-shrouded mountains were her protection and training ground, and she learned to cloak herself in the fog. Later, after she was picked up by the Demon Slayer Corps, a strange breathing technique patterned after the intangible and ever-changing nature of mist was developed.

Personality:

Seina is composed and cool, calm as ice much of the time, and drifting through life like a ghost. Yet she can be fiercely protective. For the most part, stealthy motions and grace characterize her such that even demons mostly do not get to feel her coming. She is reserved; thus sensitive, with a solid morality compass, though silent, hiding her turmoil.

Appearance:

Seina's hair cascades down her back like silvery fog in the moonlight. The pale lavender color of her eyes lends to that ghostly, otherworldly appearance. She wears a modified Demon Slayer uniform: a light, flowing white haori that, with soft gray and blue hues, reminded one of shifting mist. Her Nichiren sword has a pale, misty blade that seems almost translucent in certain kinds of light.

Breath of Mist Style: 

This style relies on the enemy's disorientation through the illusions-mist concealing one's moves and further confusing things for other people's senses. It would be perfect in ambushes but at the same time requires great precision and agility. Its forms take their names from various stages of mist and its illusions.

Nichirin Sword

It's pale white, with this unearthly shine to it. Thin, light, and agile, it's just right for quick, silent blows. Known to slice the air silently, so it would only be even more indistinguishable if Seina were to conduct an attack.

She is a senior among the Demon Slayers and teaches the younger ones how to remain cool in very stressful situations and make the most of everything that might turn in their favor. She conceals deep psychological trauma, which is a loss in the family, and secretly lives in fear of losing her loved ones, once again under a mask of coolness. She gets pretty attached to Tanjiro and others-mostly thankful for Tanjiro's empathy.

Demonic Rival: Seina's rival is a demon who has lived in darkness and shade. It's a demon that distorts by manipulating the minds of its targets. Thus, all of its powers are in total opposition to hers when dealing with mist techniques; hence, a super hot battle of feeling and strategy ensues.

Breathing Style: Breath of Mist CASUMI NO Kokyu

First Form: Silent Drifflubber.

The stance for Seina to move silently and not be detected, melded with the mist, her footsteps are barely heard by her enemies. Allowing her to further strike silently and with no warning then vanish into the fog.

Second Form: Illusion Veil.

 With it, she could create afterimages within the mist, making it indistinct from which one the actual attack would arise. These sorts of illusions threw her foes into disarray because by the time they struck at the phantoms, the real blows had long since landed from some unseen angle.

Third Form: Phantom's Grasp.

 This technique enables Seina to retreat from a field position in very short time. Mistying a trail from where she is standing, her enemies are confused with a false notion of distance while drawing closer for a sudden attack.

Fourth Form: Whispering Fog,

 With this, she calls heavy fog to shut the noise and block any possible confusion to her enemy's senses. This badly disrupts tracking of her movements as she has quite an easy time navigating through the fog, where even one can barely hear or see.

Fifth Form: Wraith's Descent

 Seina shoots off forwards in incredible speed, like a ghost cutting through the fog. The speed is so fast and airy that it's almost as though a specter were falling upon her target. The powerful form is used for finishing blows, striking with overpowering power.

Sixth Form: Ghostly Embrace

 From this stance, Seina hugs her enemy in mist; instantly, the opponent is wrapped in a vortex of fog-like nature, from which she can strike through various lethal blows that swirl around her target in as little time as the mist itself.

Seventh Form: Mist Mirage.

 She then shrouds everything around in the mist, forming some sort of fantastic landscape that distorts the apparent position of everything. This, in turn, would make her opponents mix up where they are, perhaps treading into traps and overexposure for an attack.

Eighth Form: Shifting Shadows

 When she takes this form, Seina becomes one with the shadows and mist; thus, she is practically invisible. She can appear right in front of her enemy in such a state and attack at will, which means she is truly a ghost in the battlefield.

Ninth Form: Fogbound Prison

More on the defensive side, Seina engulfs her foes in thick impenetrable fogs that trap them within the misty prison without an escape route. The fogs get that thick, cutting out one's line of vision completely, but Seina might strike from inside it with silent movements.

Tenth Form: Fleeting Wisp.

 In this form, Seina charges about like some wispy mist that barely touches the ground, fast and unsubstantial, as if she vanished and then reappeared multiple times at other locations. This is with the explicit purpose of utterly overwhelming an enemy with a storm of blows-light and quick as a wisp of fog. 

Eleventh Form: Shroud of Mist

 Seina generates a thick fog over an extensive area where none can see anything, messing with the concept of the enemy's time and space. For every few seconds they make out in those conditions, they get the impression of having spent hours; this might make them complacent and weaken their resistance.

Twelfth Form: Breath of Oblivion.

With this, final form, Seina can call upon a mist of said spirit that saps all life force from her enemy. The mist-eating everything that comes into its path-thus wraps the opponent in a smothering fog, sucking the strength out of him and turning him into easy prey. Seina strikes when the iron is hottest: the final, decisive blow within the maddening chaos of mist and shadow.