The older brother of Yume. Having a huge sister complex, he cares very deeply for her. His most prominent facial feature is a scar around his left eye. After being infected by the Pupa virus, Utsutsu gains the ability to heal his wounds and regenerate lost limbs. Thus, he acts as a living food source to satisfy his sister's hunger for flesh after she was infected by the virus.
Tropes associated with Utsutsu:
- Animal Motifs: Black butterflies.
- And Then John Was a Zombie
- Berserk Button: He goes berserk every time Yume is in danger.
- Covered with Scars: Utsutsu has many wound marks that cover almost his entire body, that are in fact burnings left from his father extinguishing his cigars on him. And a large scar across his left eye which was given to him by Yume.
- Dead All Along: Utsutsu died ten years ago, after being run over by a truck after protecting Yume with his body (unaware that she is a monster and if the truck had hit her, it wouldn't have any effect on her). She decides to bring him back to life, transforming him into a Pupa monster.
- Determinator: He will always protect Yume and nothing will ever stop him.
- Deadpan Snarker: Though "deadpan" is an exaggeration most of the time, in the manga especially he has some smartass moments.
- Deus Angst Machina/Trauma Conga Line: Starts off bad in chapter one alone, and only gets worse and worse.
- Hair Decorations: A clover hairpin, which was a gift from Yume.
- Healing Factor: At the beginning of the series Utsutsu gains regenerative powers. In order for the virus to be suppressed in Yume, Utsutsu must take a drug and have Yume feed on his flesh.
- Heroic Resolve
- Heroic Sacrifice: As a child, Utsutsu attempts to save Yume from an incoming truck, but ends up getting himself killed instead, which causes Yume to "revive" him as a monster. The fact that Yume didn't need to be protected (because as a monster, she has Healing Factor) at that point any more makes it a borderline Senseless Sacrifice, too.
- Humanoid Abomination: Thanks to Yume transforming him into one as a child.
- Meaningful Name: His name means reality.
- Oedipus Complex: He is very depressed about the fact that his mother abandoned the house. Also a plot point, given his atttraction to Yume, who is a replica of his mother.
- Ordinary High-School Student: At least until he and Yume become infected with the Pupa virus.
- Parental Abandonment: After realizing how dangerous the situation with Yume was getting, Sachiko abandoned the household. Also his father was often working for an organization and the few times he was at home he was very abusive.
- Say My Name: YUMEEEE!!
- Trauma-Induced Amnesia: Yume was the one who scarred his right eye. However, he is in denial about it and is convinced his father did it.
- Took a Level in Badass: After becoming A Pupa monster.
- Unstoppable Rage: Yume being in danger is an incredible source of anger for him. It's enough to transform into a Pupa monster and destroy everything in sight.
- You Are Worth Hell: To Yume. Especially in the manga ending.
- Voiced by: Ibuki Kido
Utsutsu's innocent and sweet younger sister and a victim of the Pupa virus. She loves her brother and always looks up to him. If she is famished, a hideous monstrosity emerges from her body like a red butterfly emerging from its pupa. Much to her horror, this proceeds to eat anything made of flesh, including humans.
It is revealed, Yume is an ancient monster that was separated from her mate Yuu and was reborn from a monster through Sachiko's womb that infected her thereby cloning her. After being reborn as a human, she forgot about Yuu and her life as a monster.
Tropes associated with Yume:
- Animal Motifs: Red butterflies.
- Becoming the Mask: At first Yume only posed as Utsutsu's sister while waiting for Yuu to save her (unaware that he was Strapped to an Operating Table), but eventually developed genuine feelings for Utsutsu.
- Dark and Troubled Past: Besides the whole thing of living by herself with Utsutsu and having absent parents... Yume is one of two ancient immortal monsters (the other being Yuu) that had the bad luck to be found in larvae form by Maria, then kept being experimented on for 30 years. She escaped and left her mate behind and impregnates Sachiko Hasegawa, being reborn as a human girl and losing her memories of being a monster.
- Hair Decorations: A flower hairpin.
- Healing Factor: As a Pupa monster.
- Horror Hunger: After the Pupa virus awakens, Yume gets chronic hunger pangs... for human flesh. If they get too severe, she transforms into a Pupa monster, and the one thing that can calm her down is Utsutsu's flesh.
- Eldritch Abomination: It was believed the Pupa virus transformed Yume into one. Then it's revealed she was a monster all along.
- The Ingenue: Yume is sweet and innocent, and Utsutsu wants to keep her that way as long as possible... Too bad she transforms into a monster whenever she's hungry. By the end of the story it turns out that it's just a facade, because she is not even human and just tries to look cheerful for Utsutsu's sake.
- Laser-Guided Amnesia: After being reborn as a human, Yume forgot about her life as a Pupa monster and her mate Yuu.
- Living Emotional Crutch: To Utsutsu.
- Karma Houdini: Yume got off way too easily for impregnating Sachiko and indirectly causing the Hasegawa's life to be a complete hell.
- Meaningful Name: Her name means dream.
- Ordinary High-School Student: At least until she becomes infected with the Pupa virus.
- Obfuscating Stupidity: She actually knew all along that she was a monster. She also remembered Yuu and apologized for abandoning him to be dissected by Maria.
- Parental Abandonment: Her parents abandoned her and her brother, leaving them to fend off themselves. And their father was abusive. She is not too affected about it like Utsutsu is. Because she is not actually related to them and is a monster without human concepts.
- Say My Name: ONICHAAAAN!!
- Troubling Unchildlike Behavior: Yume as a toddler behaved like a cold and uncaring Eldritch Abomination, eating bugs, attacking Utsutsu for no good reason and scaring the hell out of Sachiko. She only started behaving more human after falling in love with Utsutsu.
- Voiced by: Koji Yusa
Utsutsu's and Yume's cold and abusive father who works for a mysterious organization. A Combat Sadomasochist, Shiro is a bit of a psychopath and enjoys harming others, caused by being abused by Maria's grandfather thirty years ago. He looks for Utsutsu in an almost obsessive level and wants to know about the truth of the Pupa virus, since his son got infected with it.
Tropes associated with Shiro:
- Abusive Parents: He is a sadistic bastard who routinely mutilates Utsutsu, and is the one who gave him the scar across his eye. Except that Yume was the one who scarred him.
- Animal Motifs: Worms, associated with decay and negative forces within people. It's also to show he's a counterpart for Utsutsu, who's associated with butterflies. The difference is that Shiro never let go out of his traumas and became a sadistic monster instead of channeling his angst into protecting his loved ones (Utsutsu towards Yume). Thus, while Utsutsu is able to overcome his traumas and change (butterfly), Shiro never does (worm).
- Archnemesis Dad: In the first chapters. Completely averted in the end. He is just a Troubled Abuser.
- The Atoner: After he finds out that Yume is an Eldritch Abomination incarnated as a human girl, he decides to protect Utsutsu from her, in his own jerkass way.
- Badass Normal / Charles Atlas Superpower: He is able to knock out trained guards, easily disarm a nurse with a gun and survive the attacks of Pupa monsters with ease.
- Being Tortured Makes You Evil: Or in this case, really violent and only able to show affection by hurting his loved ones.
- Conveniently an Orphan: As a child he was an orphan adopted by Genjurou Imari.
- Covered with Scars: As revealed in the "Maria's Island" story, Shiro has many wound marks that cover almost his entire body. They were from his time being abused by Genjurou.
- Despair Event Horizon: Played for Laughs, but in the 4-koma after Utsutsu and Yume dissintegrate into butterflies at the end of the story, Shiro looks at the sky with a Thousand-Yard Stare and expresses his interest in chasing after the butterflies to get Utsutsu back. Even Haruka and Ryuichi know he's lost it.
- Dark and Troubled Past: It's shown that in the past, Shiro was an orphan adopted by Genjurou Imari. For years he was locked in his house, physically abused and used him as little more than a toy. He escaped after Genjurou commited suicide, only to be broke further by Maria, who claimed that Genjurou's abuse was his love for Shiro. Hence why he is so unhinged and believes that hurting those you love is the greatest form of affection.
- Expy: Stoic bespectacled man in a nice suit? Has difficult expressing his feelings? Check. Badass Normal? Check. Has a Morality Pet, whom he acts indifferent to, but the end shows that he cares about that person? Check. Gee, sounds like Soichiro Kuzuki to me.
- Get a Hold of Yourself, Man!: After Sachiko has an Heroic BSoD and remembers who Yume is.
- Good All Along / Good Is Not Nice
- Freudian Excuse: Being abused during all of his childhood definetely warped Shiro's view on giving affection to others. He even admits in Chapter 24 that he knows he's broken and doesn't know how to show proper affection.
- Hair-Trigger Temper: He often gets angry and violent for very little reason.
- Hemo Erotic: He literally equates violence with love.
- Interplay of Sex and Violence: Since he equates violence with love, he often hurts Utsutsu and Sachiko. Genjurou was the one who influenced him.
- Madness Mantra: "This is reality".
- Red Herring: He is violent and arrogant, but he is not responsible for most of Utsutsu's traumas. That's Yume.
- Papa Wolf: Towards Utsutsu in his own twisted way.
- Scary Shiny Glasses: In the anime and manga adaptations.
- Say My Name: Spends the last chapter of the manga screaming UTSUTSUUU!!
- Strong Family Resemblance: As a child he looked like a black-haired Utsutsu.
- Trauma Conga Line: His entire childhood. It'd probably be enough to drive anyone insane, really.
- True Companions: With Haruka Nico and Ryuichi Touge, his comrades from the organization he works for. He also serves as the Only Sane Man for them.
- Used to Be a Sweet Kid: Before being abused and broken by Genjurou. Just look how this went to this!
- Would Hit a Girl: He was abusive towards Sachiko, whom he accused of cheating on him. He also punched a nurse who had a gun pointed at him.
- Your Cheating Heart: He knew Yume wasn't his child, but since at the time he didn't know about the Pupa virus, he believed that Sachiko betrayed him.
- Voiced by: Mamiko Noto
Utsutsu's and Yume's sensitive mother. She cares for her son, but fears her daughter knowing she was born as a monster. After Sachiko and Shiro divorced, she went off with some other young man, leaving Utsutsu and Yume alone. Or at least that's what Shiro made them think.
Tropes associated with Sachiko:
- Break the Cutie: She was pregnant with Shiro's child and gave birth to Utsutsu. However, that day Monster!Yume escaped from the laboratory she was kept in, impregnates Sachiko and is born as a human. Knowing that the child was a monster, she had gotten to the point where she attempted to kill Yume, but she failed because Yume can't even die. She becomes more and more paranoid until she leaves the house. When Shiro finds her in the hospital after all these years, one mention of Yume's name sends it all flooding back and she flies into a blind panic.
- Cassandra Truth: Sachiko despises Yume and often claims that "that monster brainwashed her son". Nobody takes her seriously. The Reveal shows that Utsutsu's attraction to Yume was imprinted by her and Yume is basically an Eldritch Abomination.
- Dogged Nice Girl: Towards Shiro.
- Ill Girl: Not exactly ill, but she is bedridden and unstable after having to live with Yume and having tried to kill her several times.
- Madness Mantra: "This is a dream".
- Mama Bear: Towards Utsutsu.
- Offing the Offspring: She attempted to murder Yume many times, even when she was in the womb. However, Yume was a monster with a Healing Factor.
- Voiced by: Kyoko Narumi
A mysterious woman who seemed to have knowledge about the Pupa virus and is currently doing experiments regarding it. She gave Utsutsu a drug that temporarily suppresses his sister's rampage in exchange for them being examined.
Tropes associated with Maria:
- Big Bad: The closest thing the series has close to one.
- Creepy Child: As a child, she found Yuu and Yume in larvae form and was really excited at the idea of dissecting them For Science!. And evne her own family was scared of her, seeing as she dissected animals For Science!.
- For Science!: She is willing to exchange the lives of many innocent people to gain information about the effects of the virus. Even trying to impregnate herself with the virus in order to understand it better.
- It Runs in the Family: Like her grandfather, she is very devoted to her job and will not hesitate in using unethical methods.
- Innocently Insensitive: What got her scarred in the first place. She discovered her brother's porcelain dolls and realized he did....things with them from time to time. She also concluded it was due to an Oedipus Complex. Ashamed upon his secret being discovered, he threw a teapot full of boiling water on her face.
- Lack of Empathy: According to her mother and Hotoki. You really can't have anyone if you dissect creatures for curiosity.
- Karma Houdini: In the end she is not punished for trying to get impregnated with the Pupa Virus by turning into a flesh blob and assimilating with Yume. The end shows that she returns to her human form and gave birth to a Pupa larvae.
- Possibly subverted in the epilogue. From Hotoki's explanations, it could be assumed that Maria merged with the island presumably not of her own volition.
- Oblivious to Love: She's completely unaware to Hotoki (actually her brother Makoto)'s feelings for her.
- Significant Anagram: Her pen name Maria is an anagram of her real name, Ai Imari.
- Scars Are Forever: The left side of her face is scarred due to being scarred by Hotoki in her childhood.
A mysterious man who appears to show guidance to the Hasegawa siblings. Despite looking human he claims himself a monster of the red butterflies who lived for many generations on the remote island of Onigashima, explaining the reason why Utsutsu and Yume were infected.
Tropes associated with Yuu:
- Adorkable: When talking about his mate, complete with Squee!. And also his lack of common sense, such as not giving personal space to Utsutsu.
- Butt-Monkey: To the Hasegawa siblings.
- Comedic Sociopathy: Most of time, when his behavior is causing people discomfort (mostly Utsutsu), it's because of his ignorance of social rules, rather than active malice.
- Dark and Troubled Past: He is one of two ancient immortal monsters ( the other being Yume) that had the bad luck to be found in larvae form by Maria, then kept being experimented on for 30 years. Not only his mate escaped without him, she was reborn as a human named Yume and forgot his memories of him.
- Green-Eyed Monster: Towards Utsutsu for stealing away his mate. In his defense, Yume and Utsutsu bonded for 16 years, while Yuu and Yume were together for 1000 years.
- I Want My Beloved to Be Happy: After he comes to terms with the fact that his mate now loves Utsutsu and wants to live a normal life with him.
- Mind-Control Device: His tongue becomes an appendage that if it touches the ear of someone, he can give all of his memories to that person. He uses it on Utsutsu so that he could understand about the true identity of his mate. He also attempts to use it on Monster!Yume, so that she could remember her past, but it backfires.
- Strapped to an Operating Table: Yuu and his mate were discovered by Maria 30 years ago, dissecting them for her facility in researching the Pupa virus for her selfish egotism.
- What Happened to the Mouse?: Utsutsu eats him in one of his rampages and we never see him again. The epilogue shows us that because he is a Pupa monster, he regenerated easily and he's still alive.
Maria's grandfather and a painter who lived in the island of Onigashima. He only appears in flashbacks, having died thirty years ago, but he's the one who turned Shiro into the sadistic abuser he is now. He was also the one who adopted a young Shiro Onijima and tortured him to the point of insanity to get inspiration for his paintings.
Tropes associated with Genjurou:
- Dastardly Whiplash
- Dirty Old Man: Kept a young Shiro imprisoned to be his plaything.
- Driven to Suicide: He hanged himself to death.
- Lack of Empathy: You can't really have any if you get on torturing a little boy to the point of insanity.
- Mad Artist: What can you say of a man who kept an imprisoned child and tortured him just for the sake of inspiration?
- Parental Substitute: To Maria, given that we never see her parents. Also to Shiro.
- Posthumous Character: We only see him in Maria and Shiro's flashbacks.
- Whip It Good: Genjurou was fond of stripping a young Shiro naked and whipping him to lash his flesh, while claiming that the pain was the purest expression of love. Now we see where did Shiro get those strange ideas about "hurting the ones you love"...
Maria's loyal assistant. He's actually Maria's older brother. His real name is Makoto Imari and he hold incestuous feelings towards her.
Tropes associated with Hotoki:
- A Date with Rosie Palms: He lived with his father for most of his life and developed an Oedipus Complex towards his mother. To the point he collected porcelain dolls and....did things with them from time to time. After he developed feelings for Ai, he switches his preferences to dolls that look like Ai.
- Ignored Enamored Underling: To his sister.
- It's All My Fault: He blames himself for Ai's scarred face. Because he actually caused it.
- Only Sane Man
- Undying Loyalty: To Maria.
- Walking Spoiler: See all the blanked lines? There's more to him that it seems.
- You Are Worth Hell: Realizing that Ai will never look at him that way, he decides to become her assistant in order to stay close to her and help her with her dreams to become a monster.
The director of the Imari Hospital, where Sachiko is residing.
Tropes associated with Bizen:
- Mr. Exposition: He explained to Shiro about the truth of the Pupa virus and about Yume's origins.
- Improbable Age: When Maria meets him as a child, she meets a teenage Bizen, who was already a researcher of various biological diseases.
- Screw the Rules, I'm Doing What's Right!: It's implied Bizen killed Genjurou and made it look like a suicide in order to put an end to his mad art..