A pink-haired girl who has a mysterious connection with Shu, Gai, Inori and Shuichiro.
She is later revealed to be Shu's older sister. Ten years ago, Mana rescued a young Gai who she named Triton. Shu and Gai loved Mana as she was a sweet, kind person. However, unknown to Shu during that time, Mana was the first person to be infected with the Apocalypse Virus whos crystallization effects were still minimal but was making her unstable and sociopathic that she started to have incestous feelings for her brother. Mana was also the cause of the Lost Christmas incident when on that day, Mana discovered Gai was going to tell Shu the truth about her and trick Gai into shooting himself. When Shu himself arrived, Mana offer him to marry her and start a new race together but what she has become and did to Gai scared him that he rejected her and called her a monster. Heartbroken, Mana went berserk and mutating the virus and spreading it all over Tokyo before coming to her senses and destroying her body. This event effected both Gai and Shu which Gai blamed himself for not helping Mana and vowing to become stronger while Shu was traumatized on what happen to his sister that he regressed his memories of Gai and Mana.
During the 2nd Apocalypse outbreak and Shuichiro's coup d'état, Shuichiro manages to capture Mana's soul, still under the influence of the virus, and tries to resurrect her using Inori's body so that both of them will start a new race and spread the virus worldwide. However, his attempts are foiled by Shu and Gai. To free Mana's soul and be with her in her last moments, a dying Gai sacrifice himself to allow Shu to stab the crystal pod containing Mana's soul through his body, finally freeing Mana's soul from the virus.