Utsutsu and Yume Hasegawa are siblings estranged from their aloof, abusive father. One day, Yume comes across strange red butterflies, and awakens a horrible power. Utsutsu is cursed as well, and must try to protect his younger sister from forces that would love to dissect them both.
Tropes:
- Abusive Parents: Shiro Onijima is a sadistic bastard who routinely mutilates Utsutsu. But then it's revealed he's very unhinged due to being abused as a child by Maria's grandfather. And he's deluded into thinking violence is love. He even calls himself a Troubled Abuser in Chapter 24.
- Adorable Abomination: When she's not dominated by her Horror Hunger, Yume's monster form is drawn in a cutesy fashion in Chapter 17.
- 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.
- Being Tortured Makes You Evil: While being experimented on by 30 years didn't affect the personality of Yuu. Played straight with Shiro, who was abused as a child by Genjurou, Maria's grandfather.
- Bittersweet Ending: Despite Utsutsu's efforts, he cannot save Yume and he becomes a flesh-eating monster like her. They proceed to devour each other as they disintegrate into butterflies, assimilating with each other as they declare their feelings for each other. Shiro is devastated because he couldn't save his son. Sachiko is still in the hospital and blissfully unaware of Utsutsu's fate. Utsutsu's best friend, Yuhei, realizes he's never coming back. Maria survives her attempt to become a Pupa monster and gives birth to Utsutsu and Yume's larvae child. And Hotoki (actually her brother Makoto) confesses his feelings for her.
- Body Horror: Utsutsu is dissected with no anesthetic by sadistic scientists, and Yume is forced to watch. She goes berserk.
- Bugs Herald Evil: Butterflies are linked to the Pupa monsters and their metamorphic qualities are explored in a very monstrous fashion here.
- Butterfly of Death and Rebirth: The red butterflies associated with the Pupa monsters have this explicit motif, and Yume's transformation is explicitly compared to a butterfly emerging from its pupa. More explicit in the manga ending. After many sufferings Utsutsu also mutates to the point where he becomes a human-flesh eating monster just like Yume. Both naked they start eating each other, then they happily embrace for last time and both melt into a cloud of red butterflies. Only their hairpins remain.
- Cannibalism Superpower: Those infected with the Pupa virus can regenerate by consuming flesh.
- 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.
- The Chain of Harm: Shiro was abused to the point of insanity by Genjurou, and would go on to abuse his own son, Utsutsu.
- Creepy Child: Yume as a toddler behaved like a cold and uncaring Eldritch Abomination, eating birds and insects and scaring the hell out of Sachiko. She only started behaving more human after interactions with Utsutsu.
- Also young Maria. And Shiro after being broken by Genjurou.
- 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 monster.
- Eaten Alive: The fate of poor Yuu, after Utsutsu starts mutating into a monster. He survives due to his healing factor.....only to be assimilated by Maria and eaten by Utsutsu and Yume's larvae child. He doesn't come back this time.
- Eldritch Abomination: Thirty years before the beginning of the manga, Maria and her family discovered a pair of caterpillar-like creatures, which were the larval forms of shapeshifting predatory entities that would be eternally reborn. Maria dubbed the creatures Pupa, and after dissecting them to the limits of their regenerative abilities synthesized a virus from their cells. It was believed this Pupa virus transformed Yume into a monster. Then it's revealed she was a monster all along, specifically one of the Pupa who escaped Maria's lab. The Reveal also shows that Utsutsu is part Pupa, since he died several years ago when he was just a kid and was revived, all thanks to Yume.
- Eldritch Location: The entire town!
- Emotionless Girl:
- Maria was this as a child, dissecting animals and the like For Science!.
- Also Yume because of being a clone of Sachiko Hasegawa formed from the Pupa started originally as this when she was young, but interacting with Utsutsu made her more and more human.
- Foreshadowing: Yume often has flashbacks of a toddler Utsutsu lying in the ground covered in blood. That's Utsutsu's corpse, after he died as a child "protecting" Yume and shortly before she revived him.
- Freudian Excuse: Shiro was an orphan adopted by Maria's grandfather, Genjurou. For years he was locked up and tortured to the point of insanity, because seeing him injured gave Genjurou inspiration for his paintings. Hence why he is so unhinged and believes that hurting those you love is the greatest form of affection.
- Get A Hold Of Yourself Man: Shiro is very fond of giving them, complete with a No-Holds-Barred Beatdown.
- Good is Not Nice: Shiro genuinely wants to help his son to get rid of the Pupa virus inside of him. However, he is a sadistic jerkass who can only show love to his son by hurting him.
- Good Scars, Evil Scars: Utsutsu is Covered with Scars as a result of his father using him as a walking ashtray, most prominently a burn across his left eye. Turns out Yume scarred him, not Shiro but Utsutsu is in denial about it.
- Healing Factor: The Pupa virus gave Utsutsu a Deadpool-like healing factor. Good thing too, since his flesh is the one thing that can satiate Yume's Horror Hunger. It's revealed that all Pupa monsters have it and so does Yume and Yuu.
- 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.
- Horror Hunger: After the Pupa virus awakens, Yume gets chronic hunger pangs... for human flesh. If they get too severe, she transforms into a ravenous monster called the Pupa, and the one thing that can calm her down is Utsutsu's flesh.
- Humanoid Abomination: Yuu claims to be an avatar of sorts for the virus, and is revealed to be one of the two original Pupa monsters in human form. Yume is ultimately revealed to be the second original Pupa monster incarnated as a human girl.
- Incest Subtext: Whoa, where to begin?
- The subtext between Utsutsu and Yume is about as subtle as a neon sign, with her cannibalism of him being something of a metaphor for, well... sex. While Yume loves him, Utsutsu sees her more as his Living Emotional Crutch. The Reveal shows that Yume imprinted such a desire in Utsutsu's mind as a secondary-effect of bringing him back to life as a young child, but Utsutsu says it makes them no less real in his own perception.
- Shiro is a little too obsessed with his son Utsutsu and physically abuses him because of his "love is pain" philosophy. He also sees Utsutsu as a younger and more innocent version of him, which only makes him want to abuse more.
- There's also the reveal that Hotoki is Maria's brother and he has incestuous feelings towards her. Even if he has to help her into becoming a Pupa monster.
- 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 façade, because she is not even human and just tries to look cheerful for Utsutsu's sake.
- It's All My Fault: Utsutsu blames himself for having eaten Yuu during one of his monster rampages. Part of his decision to assimilate with Yume at the end of the story is not just because he loves her, but also as a way to make up for killing Yuu.
- Karma Houdini: Maria is still alive at the end of the series, not suffering any consequences for trying to get impregnated with Yume's DNA by turning into a flesh blob and assimilating with Yume. The end shows that she returns to her human form and gave birth to the caterpillar-like creature that was Utsutsu and Yume's child...
- Lack of Empathy:
- Maria is willing to exchange the lives of many innocent people to gain information about the effects of the Pupa virus.
- It runs in the family, apparently. Her grandfather Genjurou was an artist who needed love as an inspiration. Said love was torturing a young Shiro to the point of insanity. And according to Ai, there were other three orphan boys before him. Said boys died from the torture.
- Meaningful Name: Yume means dream and Utsutsu means reality.
- Morally Ambiguous Doctorate: Maria is a Mad Scientist who uses unethical methods to study the Pupa virus' victims, reasoning that they aren't human anymore.
- No Body Left Behind: Yuu disintegrated into butterflies at one point. Also, the fate of Utsutsu and Yume.
- The One That Got Away: Yuu is devastated when Yume picks Utsutsu over him. The reason being that Yuu and Yume were the original two Pupa who had been together for untold millennia, while Utsutsu is an undead human resurrected by Yume using her biomass.
- One-Winged Angel: When she gets hungry, Yume transforms into a ravenous Eldritch Abomination. Also Utsutsu, if angered enough.
- Papa Wolf: Shiro, towards Utsutsu, in his own way.
- Rape Leads to Insanity: What happened to poor Sachiko Hasegawa. The Eldritch Abomination that became Yume impregnated her by crawling into her womb.
- Sanity Slippage: Sachiko reaches the Despair Event Horizon after Pupa Yume impregnates her and is born as a human. The child, Yume, turns out to be a Creepy Child at first. Utsutsu refusing to accept that something was wrong with Yume was the final straw for her, which caused Sachiko to abandon the house.
- Say My Name: Yume's continuous "ONII-CHAN!" can match Utsutsu's often "YUME!".
- Strapped to an Operating Table: Utsutsu, in the anime's finale.
- Taking the Bullet: As a child, Utsutsu did this to "save" Yume from an incoming truck (unaware that as a monster, Yume has a Healing Factor). He died, so Yume shared some of her power with him, making Utsutsu into another monster.
- Terrible Trio: Shiro, Haruka and Ryuichi. Haruka's the pretty one, Ryuichi's the stupid one, and Shiro's the one with weird-ass powers.
- Tomato in the Mirror: Utsutsu is just another monster, just like Yume.
- The Unfavorite: Sachiko Hasegawa loves her son but hates her daughter. This is because Pupa Yume more-or-less raped her to impregnate her with itself. And it imprinted on her son, which provokes the Incest Subtext in the story.
- Unlucky Childhood Friend: Yuu, Yume's mate during her time as a Pupa monster. After bonding with Utsutsu, Yuu comes to terms with it and decides that Yume should be happy with Utsutsu.
- Womb Level: Maria herself becomes a womb-level when she was pregnant with the Pupa virus, she eventually covers the whole forest, before absorbing Utsutsu and Yume along with it.
- Yandere: Utsutsu is creepily overprotective of his sister, and more-than-a-little unhinged thanks to his father's abuse. Yume is also obsessed with her brother, partially because his flesh is the only thing that can sate her hunger.
- Also Shiro loves his son so much, that he's willing to get rid of Yume just so she won't have him.
- You Are Worth Hell: Through all the events of Pupa, not once do Utsutsu and Yume question their love for one another, or consider abandoning each other. And by the end, it's clear that they will truly be together forever.
