This page lists the characters for My Vampire Older Sister and Zombie Little Sister.
Satori AmatsuThe main character, a (mostly) ordinary high school student who lives with a vampire older sister and zombie younger sister. He's a genius with computers, being capable of creating the supercomputer Maxwell out of off-the-shelf components.
- All-Loving Hero: To the point that it's considered his best trait by his family members.
- Badass Normal: An entirely ordinary human surrounded by Archenemies, many of which could tear him to shreds effortlessly, yet he manages to hold his own.
- Clueless Chick Magnet: In the usual manner of Kamachi's male protagonists.
- Dulcinea Effect
- Generation Xerox: To his father Taizou. Both are normal humans who are oriented towards intellectual pursuits, and have love interest(s) who are superhumanly-strong Archenemies. They're also both in favor of the rights of Archenemies.
- Hollywood Hacking: Courtesy of Maxwell.
- Magnetic Hero: By the end of the second book, he has a growing faction of allies, potentially including Karen.
- Made of Iron: Being shot and beaten up by an Archenemy won't stop him from doing what needs to be done.
- Morality Chain: To his female family members, especially Yurina.
- Power Perversion Potential: He uses Maxwell, who's capable of simulating an entire city and its inhabitants, to model the Class Rep in a swimsuit.
- Red Baron: Is stated in volume 4 to be famous in the hacking community, given the nickname "Truth" by his fans.
- Teen Genius: At the age of 15, he built a supercomputer capable of modeling an entire inhabited city, which was considered a threat by the Bright Cross.
Ayumi AmatsuThe titular zombie little sister, the result of infection by Acute Zombie Powder. Originally a captive of the Bright Cross, she and Erika were freed due to repeatedly surviving the Colosseum against all odds. The two of them were adopted by Yurina and became part of the Amatsu family upon the latter's marriage to Taizou.
- A-Cup Angst: She does not like being compared to Erika.
- Attack! Attack! Attack!: Her usual battle strategy.
- Aw, Look! They Really Do Love Each Other: While she and Erika often get into fights, they nevertheless still see each other as siblings. When they first tried to escape the Bright Cross, Ayumi protected Erika during the day, even though it led to both of them being recaptured.
- Big Eater: Like all zombies in the setting.
- Little Sister Heroine
- One-Man Army: She's strong and fast enough to overpower groups of soldiers trained to fight Archenemies, and everyone and everything she bites will transform into another zombie.
- Scary Stitches: Subverted. She's covered in stitches because of the treatment she uses to prevent decay, but isn't usually someone to be afraid of.
- Uninhibited Muscle Power: The source of her strength.
- Zerg Rush: Her favorite tactic, being a zombie.
Erika AmatsuThe titular vampire older sister, a queen-class vampire. Originally a captive of the Bright Cross, she and Ayumi were freed due to repeatedly surviving the Colosseum against all odds. The two of them were adopted by Yurina and became part of the Amatsu family upon the latter's marriage to Taizou.
- Armor-Piercing Attack: She claims that her fangs can easily pierce through knight armor or a bomb-resistant suit.
- Cool Big Sis
- Elegant Gothic Lolita: Her usual dress, when not wearing her school uniform.
- One-Man Army: She's even stronger and faster than Ayumi, and has many other powers. And while she can't create vampires nearly as fast as Ayumi can create zombies, her vampires are completely under her control.
- Voluntary Shapeshifting: She can transform into animals, usually a group of bats.
- We Have Reserves: She takes this trope to extremes, having her vampire minions act as a sacrificial sunshade and throwing them away in the dozens in order to stop a flood.
Yurina AmatsuTaizou's second wife and stepmother to the three siblings. She is actually Lilith, the mother of succubi, and the leader of the Absolute Noah project.
- Demon Lords and Archdevils: As Lilith, she's an Archenemy in the traditional sense of the word, and has also given birth to several well-known demon lords.
- Healing Factor: She heals faster than regular humans do, though not to the point she doesn't need to visit the hospital in volume 5 when her stomach is heavily injured, though it's noted she'll quickly recover without leaving a scar.
- Horny Devils
- Incest Subtext: There are some... odd undertones to her interactions with Satori. Notably, it actually makes Satori himself uncomfortable.
- Lightning Bruiser: She can easily overpower both Erika and Ayumi simultaneously.
- Monster Progenitor: The mother of succubi.
- Seven Deadly Sins: As Lilith, she's considered to represent Sloth.
- Supernaturally Young Parent: She looks like a college student, yet (apparently) predates the current form of humanity.
- Walking Spoiler: It's impossible to talk about her at all without bringing up the fact that she's Lilith.
Taizou AmatsuSatori's father and a member of the Bright Cross. He's part of the organization's pro-Archenemy faction, working towards internal reform. He loses his job when the Bright Cross is dissolved at the end of Volume 2.
- All-Loving Hero: Like his son, Taizou is a very kind man that only wishes to help others. He wishes he could have saved Charlotte Fregula even after she attacked him and his family.
- Badass Normal: Managed to defend himself from over 200 of Charlotte Fregula's bullets using nothing but a tarp. The sight of this is so unbelievable Charlotte herself is left completely baffled as to how he can compete with her predictive ballistic calculations, and even Satori questions whether his dad has a power like the female members of their family.
- Dating Catwoman: A member of the Bright Cross who marries an Archenemy. Downplayed, since he doesn't actually hate Archenemies unlike most of his colleagues.
KarenA whimsical woman dressed in a bunny costume, and a member of the Bright Cross. She is actually a Valkyrie and one of the organization's leaders.
- Authority Equals Asskicking: One of the Bright Cross' leaders, and a powerful Archenemy capable of effortlessly curb-stomping a group of Archenemies and Badass Normals.
- Bling-Bling-BANG!: When she fights, she uses a spear and shield made of solid gold.
- Expy: Of Karen, a character from another of Kamachi's series. They have the same name, appearance and many of the same mannerisms, in addition to being Well-Intentioned Extremists. One of the crossover side stories implies that Valkyrie Karen is a direct reincarnation of Bunny Girl Karen in a different dimension.
- Fantastic Racism: Being a member of the Bright Cross. Actually subverted, as she's even an Archenemy herself.
- Lightning Bruiser: When she reveals her true nature as a Valkyrie. She can wield weapons literally made of solid gold, knock bullets out of the air, and throw her shield with enough force to cause an explosion on impact.
- Playboy Bunny: Her costume.
- Shameless Fanservice Girl
- Valkyries: Her true nature.
- Walking Spoiler
- Well-Intentioned Extremist: Her true goal is actually to maintain an uneasy coexistence between humans and Archenemies, by keeping human bigotry under control and killing any problematic Archenemies.
Tamago ItouA sniper for the Bright Cross, who specializes in using a fully-automatic sniper rifle that fires subsonic ammunition. He is Helen's older brother.
Charlotte FregulaOne of the leaders of Absolute Noah and the identity used by Echidna, the snake woman that birthed some of the most legendary monsters in Greek Mythology.
- Guns Akimbo: Wields two submachine guns that fire small herbit crabs that spin the tip of their shell like a drill to stab deep into the targets flesh and then use their claws and mouth to tear through their flesh from within.
- Improbable Aiming Skills: Thanks to her improved brain Charlotte can make ridiculous physical calculations on the fly to perform these, including ricocheting her bullets multiple times to target people behind cover.
- The Mole: Charlotte turned out to be part of another secret group, known as the Hidden Cloud. She had inflitrated and made herself a key part of Absolute Noah in order to destroy it and trigger the Calamity.
- Monster Progenitor: The mother of several legendary Greek monsters like Cerberus, Orthrus, the Nemean Lion, the Hydra, Chimaera, Karkinos, etc...
- Wetware CPU: Charlotte has remade her body several times, and the results of these customizations include the optimization of her brain chemicals, hormones, and chemical reactions in the blood that turned her brain into a supercomputer which is used as the planetary simulator of Absolute Noah.
SylpheedAn unnamed Sylpheed member of Absolute Noah.
- Elemental Embodiment: A Sylpheed (a female Sylph) is the anthropomorphized version of the alchemic element of wind.
- Our Fairies Are Different: Sylpheed has the appearance of a small fairy the size of a human finger.
- Size Shifter: Sylpheed has the ability to shrink in size. She usually takes advantage of this by first accelerating at high speeds in her regular form before shrinking to focus the kinetic energy on a small point, essentially turning herself into a living bullet.
- Super Speed: If given enough time and space to accelerate she can reach supersonic speeds.
Class RepThe representative of Satori's class, whose real name has yet to be mentioned. Also Satori's childhood friend, who lives next door.
- Badass Normal: Played for laughs. She's proficient in several martial arts, but this is portrayed as making her more capable of punishing Satori for his perversions.
- Childhood Friend
- Class Representative
- Dhampir: Is involuntarily turned into one in Volume 3.
- Everyone Calls Him "Barkeep": Literally every other character, even Yurina, calls her "Class Rep".
Setsuna YuubariMinori's girlfriend and her second in the Colosseum.
- Master of Disguise: She disguises herself as Hinoki in order to approach Satori outside of the Colosseum, using a Leanan Sidhe's power to weaken both Satori and Helen.
Taori MagatsuTaizou's first wife and Satori's biological mother. She divorced Taizou prior to the start of the series over the latter's affiliation with the Bright Cross (unaware that he was trying to reform it from the inside). She returns in Volume 3, having remodeled her body into an incredibly powerful Archenemy hunter.
- Ambiguously Human: While she certainly isn't a normal human anymore, it's not quite clear if she's an Archenemy, either. Yurina's comments suggest that she may actually be closest to a Saint from A Certain Magical Index.
- It's Personal: She absolutely hates Yurina for (in her perspective) stealing her place in her family.
- Mix-and-Match Weapon: Her weapon is a giant triple-bladed chainsaw with an oversized crossbow attached to the handle. The chainsaw can cut down entire trees with ease, while the crossbow fires bundles of bolts that split after firing to bombard an area.
- The Needless: She's imprisoned for several years without any food, water or even oxygen, yet is still strong enough to fight Yurina.
- Super Strength: To the point that she can easily wield a weapon weighing over 70 kilograms.
AnastasiaA white hat hacker who goes by the Red Baron of Maiden, first introduced in Volume 4. Turns out to be one of the Archenemies living in Las Vegas.
- Child Prodigy: Only 11 years old, but she's skipped several grades to enter a certain university at Massachusetts and is considered a notable hacker that has caught the attention of both the CIA and the NSA.
- Healing Factor: What ultimately gave away her identity to Satori was that she began healing unnaturally fast from having her stomach pierced by a piece of rebar.
- The Fair Folk: Anastasia is a Silky, a type of fairy that likes to wear silk dresses, helps out with all the housework, and protects the home, but that will drive out any master they don't like even if it gets them hurt. Basically the European version of a Zashiki Warashi and similar to maids, which embarrasses Anastasia and causes her to hide her true nature.
- Playful Hacker: She deliberately attacks the systems of government and corporations, infecting them with a harmless test virus called Weather Report that informs them that they need to update their security.
Helen ItouAnother student who goes to Satori's school, who's actually a Circe witch. She's kidnapped by the Bright Cross, and Satori's efforts at helping her drive the plot of the second volume.
- Baleful Polymorph: Her potions allow her to do this to others. Interestingly, the few times this happens it's actually beneficial to the person being transformed, as it allows them to survive the Bright Cross' execution methods.
- Heart Is an Awesome Power: Her sole power is to create transformation potions, but it makes her one of the most versatile characters in the setting. She can heal, strengthen herself and others, and defeat people non-lethally.
- Our Witches Are Different: Helen is a Circe witch, who specializes in brewing potions that transform living things.
- Thou Shall Not Kill: She adamantly refuses to kill anyone, even in self-defense.
- Voluntary Shapeshifting: By drinking her own potions, she can transform parts of her body into those of various kinds of animals.
Hinoki KuroyamaA mermaid who's forced to fight in the Colosseum, and Helen's first opponent.
- Compelling Voice: She can control anyone who hears her voice.
- Dishing Out Dirt: Unusually for a mermaid, she's capable of manipulating rock.
- Our Mermaids Are Different
- Selkies and Wereseals: She wraps her long hair around her body, forming a fish-like tail, in a manner compared to a selkie.
Minori HanesakiA Leanan Sidhe who's forced to fight in the Colosseum, and Helen's second opponent. She is also Setsuna's girlfriend.
- Brought Down to Normal: Helen uses a potion to remove her traits as a Leanan Sidhe, so that she can be with Setsuna without killing her.
- Heroic Sacrifice: She wants to let Helen kill her, so that her life-draining doesn't kill Setsuna. It's thankfully subverted when Helen uses a potion to turn her into a human, removing the need for her to die.
- Invisibility / Intangibility: She can't be seen or touched by anyone aside from her lover(s).
- Life Drinker: Her power as a Leanan Sidhe. It's also involuntary, which she hates as it means she'll kill Setsuna eventually.
- Our Fairies Are Different: She's specifically a Leanan Sidhe. She can't be seen or touched by anyone except those she designates as a lover, and she drains life force from them whenever she gives them inspiration.
Yukie MuramatsuA dark elf who's forced to fight in the Colosseum, and Helen's third opponent.
- Half-Human Hybrid: She has a human father.
- Our Elves Are Different: She's a combination of Norse and English mythology about elves, with her racial name and appearance coming from the former and her powers coming from the latter.
- Shock and Awe: The real nature of her elfshot ability is an electric charge, apparently produced from her body. She can conduct it through iron powder shot from her bow (giving the appearance of an invisible arrow) or through a melee weapon.
LeviathanThe legendary sea monster that together with Behemoth was created by God to feed the apocalypse's survivors. Leviatahan is a demon lord and the leader of a faction of marine Archenemies.
- Demon Lords and Archdevils: As a demon lord Leviathan is one of the strongest Archenemies in the world.
- Green-Eyed Monster: Fitting its status representing Envy, Leviathan's reason to hate and attack Lilith is that she has what it cannot, the love of a family.
- Seven Deadly Sins: Leviathan is one of the demon lord candidates to represent the sin of Envy.
- Telepathy: Leviathan can emit a pulse that interferes with the brains' electric signals, allowing it to communicate with others telepathically or even control their bodies. Satori discovers that he can protect himself by improvising a helmet with a thin protective layer made of lead that blocks the pulse.
- Threatening Shark: Leviathan has the shape of a giant shark the size of a small submarine, described as more than 30m long.
MaxwellA simulator built by Satori out of video game consoles, designed to simulate the effects of natural disasters.
- Clingy Jealous Girl: Expresses jealousy towards Laplace when Satori takes her in, and is offended when someone offers to help Satori by gathering information on Archenemies, making Maxwell claim she's his information gathering agent, and thus, any help is unnecessary.
- Cyberspace: Using mind input devices, it's possible for users to take part in the simulations directly. This serves as the stage for the events of Volume 1.
- Meaningful Name: Named for James Clerk Maxwell, who came up with the concept of "Maxwell's demon".
- Samus Is a Girl: Volume 3 reveals that, despite the masculine name and lack of a biological sex, Maxwell identifies as female.
LaplaceA simulator built by the Bright Cross to handle their classification of people based on potential. She undergoes a HeelFace Turn in Volume 2 and joins Satori's side.
- HeelFace Turn
- Meaningful Name: Named for Pierre-Simon Laplace, responsible for several important mathematics concepts such as Laplace's equation and the Laplace transform.
- Redemption Demotion: Due to being unable to retrieve all of Laplace, Satori has her split up into 12 parts. Eleven are decoys, with the smallest part (containing Laplace's personality) the only one he keeps. It's implied that Maxwell may have deliberately invoked this trope, to avoid being supplanted by a more powerful AI.
- Shrinking Violet
- Samus Is a Girl
Ghost CatThe security server of the Peace Committee Convalescent Hospital, an abandoned hospital in Kukyou City that belonged to a minor organization separate from the Bright Cross Foundation that dealt with Archenemies. After the hospital was abandoned Ghost Cat continued their anti-Archenemy research and plans. After defeating her and neutralizing her as a threat Satori recovers her from the hospital.
- HeelFace Turn: Ultimately recovered by Satori and added to his AI support team
- Redemption Demotion: Like with Laplace, Satori only recovered one blade server from the abandoned hospital.
- Samus Is a Girl: Like Maxwell and Laplace, though more obvious given that she chose to use a female voice to taunt Satori when she thought she had won.
- Weak, but Skilled: Ghost Cat cannot compete with either Maxwell or Laplace's specs as a pure simulator, but it's noted by Maxwell to have a superior ability at controlling and providing parallel instructions for drones and other unmanned weapons.