Movie
Description
Yuuji Sakai is a high school student who discovers he is already dead, existing as a Torch—a fading remnant of a human. He is a unique Mystes, containing the Treasure Tool called the Midnight Lost Child (Reiji Maigo), which restores his Power of Existence every night at midnight. This allows him the potential to live a regular lifespan, provided his power does not deplete before each restoration.

He initially exhibits a kind, self-sacrificing, and compassionate personality, often prioritizing others' well-being over his own. This behavior defies the typical selfishness of Torches, causing both confusion and annoyance in the Flame Haze Shana. Though generally easygoing, he can be shrewd and is capable of sharp criticism, notably challenging Shana early on for her lack of empathy and nihilistic outlook. He possesses a keen intellect and demonstrates a remarkable ability to remain calm and think logically in emergencies, often devising unconventional solutions—a trait respected by allied Flame Hazes.

He remains oblivious to the romantic feelings Shana and his classmate Kazumi Yoshida develop for him, leading to interpersonal tension. This obliviousness stems from his own sense of depreciation as a Torch and his view of Shana as unattainable, causing him to distance himself from their former closeness.

A significant fear is the potential loss of the Midnight Lost Child and his subsequent disappearance. Driven by this fear and feelings of powerlessness against powerful Denizens, he undergoes rigorous training to better defend himself and others. He gains combat abilities, including the power to cast Power of Unrestraint and wield weapons like Blutsauger, infusing them with his own power. Over time, his personality shifts, becoming colder, more indifferent, and noticeably more ruthless—exemplified when he kills duplicates of a Denizen with his bare hands and incinerates the rest.

His character undergoes a drastic change after he mysteriously vanishes on Christmas Eve and reappears merged with the Snake of the Festival, a powerful Crimson God and leader of Bal Masqué. This merger makes him the substitute body for the Snake and the new leader of the organization. He gains immense power and the ability to create silver and black flames. His personality becomes ruthless, manipulative, and outwardly confident, often displaying cruelty—such as deliberately causing a mental breakdown in the Flame Haze Margery Daw by revealing painful truths and coldly exploiting Kazumi Yoshida's feelings for strategic purposes.

As leader of Bal Masqué, his stated goal, influenced by the Snake of the Festival, is to create a new world called Xanadu—a paradise where Crimson Denizens can live peacefully without consuming human Power of Existence, thereby ending the eternal conflict with Flame Hazes. He claims these actions are ultimately for protecting everyone and being with Shana, whom he confesses his love for before imprisoning her and stripping her of her powers.

His methods and allegiance are opposed by Shana and her allies, leading to a final conflict. During this battle, it is revealed that his plan could have been achieved with trust and cooperation rather than force and manipulation. He realizes his fixation on his goal caused him to neglect and hurt Shana, the person he most wanted to benefit. Wracked with guilt, he initially believes he must atone for his actions alone by wandering Xanadu.

After being defeated by Shana and accepting her forgiveness and love, he undergoes a transformation. With the help of a new Unrestricted Spell called Grammatica, his existence is restored, making him human again. He then uses another spell to restore the humans in Misaki City whose existence had been absorbed by Denizens before departing for Xanadu with Shana.

His appearance changes throughout his journey. Initially, he has neck-length dark hair and a fair complexion, typically wearing his high school uniform. After merging with the Snake of the Festival, his hair becomes waist-length—though it can change form into a black scarf or bolo tie—and he gains red and black armor called Bakuyagai, which he continues to use even after separating from the Snake.