Mana Ouma has long, whitish-pink hair with a white flower pin on the left side of her head. Her bangs are parted in the middle, with two strands tied in the front. She has striking orange-red eyes and a delicate yet captivating appearance. In her reincarnated form, she closely resembles Inori Yuzuriha, emphasizing their connection.

Mana typically wears a light pink dress that complements her hair. In flashbacks, she is occasionally seen in a white uniform or a pink winter coat. After her reincarnation, her outfit changes to a black dress with a deep cut down the middle and a violet skirt, reflecting her transformation.

Initially, Mana Ouma is portrayed as a kind and affectionate girl, acting as a gentle and loving older sister to Shu Ouma. However, after becoming infected with the Apocalypse Virus, her personality undergoes a drastic change, turning her into a sadistic and manipulative individual. Under the virus’s influence, she attempts to force Triton (Gai Tsutsugami) to take his own life so she can be with Shu. Her obsession with “tying the knot” with Shu stems from her desire to mix their genes and create a new world together. However, when Shu resists her advances and pushes her away, it triggers a catastrophic event on December 24, 2029, later known as “The Lost Christmas” incident.

By Episode 12, Mana is revealed to be deeply resentful toward Shu for rejecting her, showing a willingness to harm him. While possessing Inori Yuzuriha, she displays an even more ruthless nature, brutally killing anyone who tries to harm Inori while smiling. Despite her hostility, she still expresses love for Shu, as seen in Episode 18, where she attempts to force herself on him. She also looks down on Inori, referring to her as a “fake”, further reinforcing her belief that only she is worthy of Shu.

It is ultimately revealed in Episode 20 that her kind and caring personality was merely a façade. Having been infected with the Apocalypse Virus since the age of five, Mana had long been under its influence and had chosen Shu as her “Adam” even before he was born, sealing her role as a central figure in the virus’s grand design.

Mana Ouma lived with her parents in Oshima, where she first discovered the meteorite that carried the Apocalypse Virus. Upon coming into contact with it, she became infected, and as the virus spread through her body, it began affecting her mind. Under its influence, she developed unnatural abilities and, as part of the virus’s influence, chose her unborn brother, Shu Ouma, as her destined mate—her “Adam.”

After the death of their mother, Mana and Shu were left alone on Oshima. During the summer before Lost Christmas, Mana took Shu to her favorite spot on the island, where they encountered Gai Tsutsugami, who was drowning at sea. They saved him, and Mana playfully nicknamed him “Triton”, explaining that she found him by the ocean. The three spent the rest of the summer together before leaving for Tokyo when their father remarried.

Following their move, Mana and her new stepmother waited in a church for a family gathering. She manipulated Haruka Ouma into leaving to search for Kurosu Ouma, convincing her that he had likely stayed behind due to his workaholic nature. With Haruka gone, she turned her focus to Gai, tricking him into shooting himself before using his blood as lipstick, further embracing the Apocalypse Virus’s control over her. With her plan in motion, she attempted to marry Shu, forcing him into a ritual that would complete their union. However, when Shu noticed parts of her hair crystallizing, he instinctively recoiled in horror, calling her a “monster.”

This moment of rejection shattered Mana’s control, forcing her to confront the reality of the virus’s influence over her. Panicked and desperate, she begged for help, but Shu, still a child, was too afraid to approach her. Overcome with emotion, Mana lost control of her powers, triggering the catastrophic event known as “Lost Christmas.” The outbreak of the Apocalypse Virus resulted in widespread devastation, leading to Mana’s physical destruction. However, fragments of her consciousness and influence remained embedded within the Voids of those affected by the virus, ensuring that her presence would continue to shape the events that followed.

As patient zero of the Apocalypse Virus, Mana Ouma possesses complete control over the infection, utilizing its crystallization effects to achieve abilities far beyond those of any other infected individuals. Even as a child, she demonstrated the ability to form and manipulate crystals in her hand. However, after being rejected by Shu Ouma, she triggered the Lost Christmas event, unleashing the virus at an unprecedented rate and crystallizing thousands of people within seconds. Due to her still-developing powers, this event resulted in her falling into a coma.

Years later, after regaining her strength, Mana’s abilities evolved to a far greater scale. She displayed terraforming abilities, covering entire areas in crystal formations and manipulating them at will. She could use these crystals as weapons, shaping them into large spikes for impalement or restraints to trap her enemies. Even after her second death, her power continued to manifest through her vessel, Inori Yuzuriha, whose exposure to multiple Voids which contained fragments of Mana’s consciousness further enhanced her abilities. While inside Inori, she could generate crystal spikes from her body, using them lethally, such as when she stabbed Arisa Kuhouin. When channeling Mana’s power, Inori also took on a monstrous form, significantly boosting her speed, strength, and endurance, allowing her to destroy multiple Endlaves with ease.

After fully reincarnating through Inori, Mana’s abilities reached their peak. She gained the capability to spread the Apocalypse Virus on a global scale, allowing her to instantly crystallize people anywhere in the world.

Void
In the final episode, Gai Tsutsugami extracts Mana’s Void, which closely resembles Inori Yuzuriha’s Singer’s Sword but with a darker complexion, symbolizing her overwhelming power.

The name Mana (真名) is composed of “ma” (真) meaning “real” or “genuine” and “na” (名) meaning “name, noted, distinguished, or reputation.” Her surname, Ouma (桜満), combines “ou” (桜) meaning “cherry blossom” and “ma” (満) meaning “fullness, enough, or satisfy.” Together, her name could symbolize a distinguished or genuine existence, while her surname may represent a fleeting yet powerful presence, much like cherry blossoms in full bloom.