This is a partial character sheet for Kamen Rider Double. Visit here for the main character index. Subjective trope and audience reactions should go on the YMMV page.
Ryubee Sonozaki/Terror Dopant
Portrayed by: Minori TeradaThe paterfamilias of the Sonozakis, he masterminds the entire Gaia Memory operation, using it to weed the weak-minded adults of society. As the Terror Dopant he can produce deadly liquids, literally make people fearful, and summon a dragon from his headdress. After Double defeats him with the Double Xtreme Maximum Drive, he returns to the burning mansion, dying in a maddened state.
- Affably Evil: Somewhat.
- Ambition Is Evil: Ryubee's ambitions cost him and the rest of his family everything. Some of them even die more than once for his goals.
- Big Bad: He's the driving force of the primary antagonists, though he ended up getting supplanted as the final fight by Jun Kazu.
- The Chessmaster: Everything he does is in the name of his goal of making everyone on the planet connected to the True Gaia Memory like Philip was to prevent an extinction event from ever occurring.
- The Don: The Sonozaki family operate Museum much more like a Mafia than a Yakuza, despite operating out of Japan.
- Embodiment of Vice: Greed, seen in his lavish lifestyle as king of Futo's underworld and the ambitions that tear his family apart.
- Evil Laugh: Not just a habit of Ryubee's, but an integral part of the Terror Dopant's schtick.
- Nice Hat: Has a Headpiece of Doom when in his Dopant form. It can even turn into a floating monster the size of a house!
- Papa Wolf: On the surface, his behavior towards Wakana is this, in contrast to his treatment of Saeko. The truth is more complicated.
- Sanity Slippage: Aside from the obvious moment before his death, he also was merely a bad father before Raito died and was reborn as Philip. It's only after that incident that he truly started to become monstrous.
- Social Darwinist: While using the Gaia Memories to weed the weak-minded out of society isn't his aim per se, he certainly doesn't mind it as a consequence.
- Stealth Hi/Bye: Capable of these without involving Gaia Memories.
- Supernatural Fear Inducer: His Terror Memory's main power, creating fear in others via a fear-inducing ooze that he produces in vast quantities, resembling an oil spill.
- Tragic Villain: His Fatal Flaw of ambition ultimately costs his family their happiness and unity, as well as his sanity and, ultimately, his life, as he spends his final moments laughing like a madman in his own burning, crumbling house. He'd be a good fit in a William Shakespeare play.
- Villainous Breakdown: His Terror Memory being destroyed along with his entire scheme being thwarted just as it was about to succeed causes him to snap. He dies dancing blissfully as the Sonozaki mansion is burning to the ground around him, laughing insanely.
- Well-Intentioned Extremist: Driven by a fear that humanity would one day become just as extinct as all the long-gone species in his museum, Ryubee set about a plan to meld humanity with the Earth itself.
- Xanatos Speed Chess: Implied between him and Shroud.
- You Have Outlived Your Usefulness: To his wife, of all people.
Saeko Sonozaki/Taboo Dopant/Level 3 Rnote -Nasca Dopant
Portrayed by: Ami NamaiRyubee's elder daughter, assisting her father in the Gaia Memory business. She marries Kirihiko the Gaia Memory salesman. As the Taboo Dopant she can fly and shoot energy. She turns on him, killing him after he has a HeelFace Turn. She then got interested in Dr. Shinkuro Isaka, the Weather Dopant, before his untimely demise. After losing the Taboo Memory to Mick, she recovers the Nasca Memory and uses it, unlocking level 3 until she is defeated by Wakana's Claydoll Xtreme.
- Black Widow: She's killed most of her fiances and husbands off, including Kirihiko.
- Cartwright Curse: Saeko just can't catch a break with her love interests, each of them dying over the course of the series. Mind, Kirihiko was her fault entirely, but Isaka and Jun were definitely out of her hands.
- Chickification: She goes through this after taking up with Isaka, though it seems like she's doing it on purpose to make herself seem more attractive.
- Embodiment of Vice: Lust, going through three romantic interests over the course of the show. It's stated that she's gone through many, many more before them, disposing of her partners once they bore her.
- Enemy Mine: Versus Utopia.
- Even Evil Has Standards: Even Saeko is rather uneasy about Isaka modifying Wakana's Driver to not let her safely transform.
- Evil Genius: Also a bit of The Dragon, given that she killed off the Boss in the premiere and fights Double at times.
- Manipulative Bitch: From the very beginning, her "romance" with Kirihiko was an experiment to decipher the Nazca Memory's power by sacrificing her "husband" to it to see how far he could push it until he dies.
- Meaningful Name: Saeko means cold child, and she spends the series being cold and antagonistic to Wakana.
- Nevermind how it's pronounced...note
- Navel Window: The Taboo Dopant appears to be wearing a red dress with a cutout exposing her navel.
- Palette Swap: After losing the Taboo Memory to Mick and having her Gaia Driver destroyed, she starts to use Kirihiko's Nasca Memory, proving far more compatible with it than Kirihiko ever was.
- Pyrrhic Victory: While she manages to survive the downfall of the Museum and Ryubee's death, she loses the Nasca Memory after being defeated by Claydoll Xtreme.
- Red Is Violent: Her Dopant forms are primarily colored red, and she's a violent Black Widow and a powerful fighter.
- The Starscream: For most of the first two acts of the series, it was hinted that she had bigger plans for the Memories beyond those of her father. "Beyond R", the conclusion of the second act, shows her and Isaka first plotting to take Ryubee down and then making their move. Isaka didn't survive, and Saeko went on the lam.
- Thicker Than Water: Subverted for the majority of the series; though Saeko doesn't openly hurt her family for the most part, she harbors a very strong grudge towards Wakana, and she develops similar feelings towards her father in turn. However, once the family and the Museum is in ruins, and Jun attempts to retrieve Wakana to forcibly restart the Gaia Impact attempt, she gives her life attempting to stop him, making Wakana leave for safety.
- The Unfavorite: She views herself as this as being the eldest meant she wasn't allowed to really indulge herself in her own interests. It's not clear if she actually is though.
- Unholy Matrimony: Marries Kirihiko early in the show, but doesn't love him any more than the various other suitors she's wed and killed. Her romance with Isaka, however, is genuine.
Wakana Sonozaki/Clay Doll Xtreme Dopant
Portrayed by: Rin AsukaThe younger daughter of Ryubee, she is a popular idol around Futo, to the point of having her own radio show. Is the least interested in running the family business. As the Clay Doll Dopant, she can shoot fireballs from her arm and reform after being broken into pieces. Her Driver was tampered with by Isaka, which now left her mind open to the madness induced by Gaia Memory usage. Her father also manages to fully turn her to evil just as she plans on escaping Futo with Philip, turning her into the new Dragon. She seemingly dies in the wake of the Sonozaki Mansion's destruction, yet her body was recovered by Jun Kazu to be used in Foundation X's plan.
- Astonishingly Appropriate Appearance: In her first appearance, Wakana wears her hair in a style very similar to her Claydoll Dopant form's head design.
- Bitch in Sheep's Clothing: Before she underwent Character Development.
- Brainwashed and Crazy/Mind Rape: What her father does to her.
- Catchphrase: "Why must you anger me?". Also, see Verbal Tic below.
- Chewing the Scenery : She copies her father's "XTREEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEME!" when she unlocks her Super Mode.
- Creepy Doll: She is one as the ClayDoll Dopant.
- Dark Chick: Given that she's the least interested in running the family business... Until Saeko rebels, and Ryubee promotes Wakana into The Dragon.
- Devil in Plain Sight: Despite being one of the Museum Dopants she has fans in Shotaro and Philip, who listen to her radio show.
- Driven to Madness: After her Driver is tampered with by Isaka, she gradually becomes mad. While Wakana adjusts to avoid the impairing effects of this, her personality takes a permanent turn for the worse.
- Embodiment of Vice: Envy, both in the sense of wanting to escape her family's obligations and her eventual usurpation of the Gaia Library for herself. It's appropriate that her Super Mode comes with a whole lot of green light.
- Evil Costume Switch: Before being brainwashed, she used to wear bright-colored clothes. After that, she switches to dark colors.
- Evil Sounds Deep / Power Makes Your Voice Deep: As the Claydoll Xtreme Dopant, her voice is way, waaaaayy deeper than normal. Fitting, since this form is so monstrously-powerful that the Kamen Riders simply can't beat it normally.
- HeelFace Revolving Door: Following the The Radio Q arc (#13-14), Wakana began to regret being involved with the Museum and being the Clay Doll Dopant. Then during the The P Game arc (#25-26) she directly attacks her sister due to Isaka's influence. Then in the Client X arc (#37-38), she finally is on the cusp of her HeelFace Turn when something happens thanks to Ryubee and she becomes completely evil. Then by the end she gives her life to allow Philip to come back to life.
- Idol Singer: Gets her own Defictionalized single release with "Naturally".
- Magikarp Power: Clay Doll seems to be the weakest of the Gaia Memories used by Museum, primarily useful for its regenerative ability and suffering the humiliation of being unable to hit even an untransformed Kirihiko. Claydoll Xtreme, meanwhile, is so monstrously powerful that not once do the Riders ever stand a chance against her.
- Nightmare Face: Claydoll has a disturbingly human-like face with lifeless, glassy eyes.
- One-Winged Angel/Evil Counterpart: The Gaia Progressor she gains from her father grants her Claydoll Xtreme form, which is much more powerful and grants Wakana access to the Gaia Library.
- People Puppets: Was the victim of one such attempt, by way of the Puppeteer Dopant - her Dopant form is named Claydoll, after all.
- Rich Bitch: Until she mellowed out in "The Radio Q", that is.
- Talking the Monster to Death: By the end of the show, this is the only option for dealing with Wakana, who's so powerful that beating her in combat is impossible. The one who does the talking isn't Shotaro or Philip, though, but Shroud.
- Verbal Tic: *tch* , complete with close-up.
Kirihiko Sonozaki (né Sudo)/Nasca Dopant
Portrayed by: Yuki KimisawaA promising Gaia Memory salesman who became engaged to Saeko. In his childhood, he designed the famous mascot Futo-kun, based on a windmill. Marrying into her family, he quickly becomes a Museum commander, assisting Saeko in administering the family business. As Nasca he has Super Speed, flight, and fencing skills. He's the first Museum member to perish, as his Nasca Memory begins to kill him when he unlocks too much of its power. He makes a final appeal to Saeko to make a HeelFace Turn with him, and she finishes him off.
- Alas, Poor Villain: The Farewell N arc generates plenty of sympathy for Kirihiko, and ends with his perishing.
- Bring My Red Jacket: The cravat that Kirihiko wears has a red mark on it right over his chest. It's practically a bullseye for the attack that eventually kills him.
- The Chew Toy: The net movies have him slapped by his sister in-law, insulted by his wife, attacked by his familys pet, assaulted by Jun Kazu and blown away by his son. The one guest who gets along with him is Isaka, due to their shared resentment of Kazu - and even Isaka injures him.
- Deadly Upgrade: Upon taking the Nasca Memory to Level 2, Kirihiko begins seizing up whenever he tries to use it, and then even when he's not using the Memory, which Ryubee reveals to be the result of his excessive training and poor compatibility with the Nasca Memory leading to one of these. Worse yet, Ryubee and Saeko knew this would happen to him and gave him the Memory deliberately knowing it would kill him. Judging by the pain he's in, what Saeko does to him might qualify as a Mercy Kill by comparison.
- The Dragon: During his tenure, Kirihiko is the most active Museum member by far when it comes to engaging Double in direct combat.
- Embodiment of Vice: Pride, exhibited in his Noble Demon tendencies and his cocksure attitude, even dodging Clay Doll's attacks without transforming at his wedding just to show off the fact that he can.
- Even Evil Has Standards: Kirihiko draws the line at giving a Deadly Upgrade to kids to see what will happen.
- Fanservice: He's stark naked (save for his Memory Driver) when he's given the Nasca memory and his ass is in full view of the camera.
- HeelFace Door-Slam: He tries to convince Saeko to join him, but she finishes him off. Though in KAMEN RIDER: memory of heroez, he gets to pull a Heroic Sacrifice alongside Ankh.
- The Maiden Name Debate: Inverted - he takes Saeko's family name after their marriage because she is his social superior.
- Scarf of Asskicking: Has two, similar to Kamen Rider V3.
- Super Speed: Kirihiko's training with the Nasca Memory eventually unlocks this power for him. Unfortunately for him, that training pushed him past the limit of how much of the Memory's power he could handle.
- Unwitting Pawn: He was always meant as a sacrificial pawn to test how far he could push Nazca, and only learned this after he began dying from it.
- Well-Intentioned Extremist: Loves Futo as much as Shotaro does, yet is willing to use Gaia Memories to destroy those who wish it harm.
- You Have Failed Me: Saeko showed increasing displeasure over his failure to defeat Double in the form of both verbal and physical abuse. She forgives him for it, but it turns out he'd failed her from the very beginning, and she gave him the Nasca Memory knowing it would kill him.
Shinkuro Isaka/Weather Dopant
Portrayed by: Tomoyuki DanShinkuro Isaka is a benefactor of the Sonozaki family and high-ranking member of the Museum. He is the wielder of the Weather Memory, responsible for the murders of Ryu's family. Isaka appears on the scene after Kirihiko's death and becomes a love interest to Saeko, initially working as the head doctor of a hospital until Ryu exposes him as a Dopant and he is forced to go underground at the Sonozaki mansion. He is killed when, after Accel destroys his Weather Memory in Trial Mode, Isaka is consumed by the multiple Memory ports all over his body.
- Arch-Enemy: To Ryu.
- Arc Villain: From The I Doesn't Stop to Beyond the R.
- Big Eater: Having multiple memory drives supercharges his metabolism, requiring him to have a high calorie intake.
- Character Tics: Licking his lips.
- Eat the Dog: Near the end of #28, Isaka thinks about how hungry he is and begins staring at the cat. Fortunately, Mick comes through it unscathed.
- Embodiment of Vice: Gluttony, both in his Big Eater tendencies and his endless hunger for more powers than even his Weather Memory grants him.
- Evil Cannot Comprehend Good: After Accel finally destroys his Weather Memory, he's left unable to fathom how Ryu managed to defeat him without his hatred, not realizing it was his determination to save Isaka's captive that gave him the strength to master the Trial Memory and win.
- Fetish: Is interested in Saeko's body only when she is in her Dopant form.
- Informed Ability: Supposedly has gained the power of numerous Gaia Memories, yet he always relies only on his Elemental Powers. That said, he's been shown to resist multiple Memory Breaks, albeit not unscathed, and even compared to a normal Dopant he seems unusually powerful.
- Laser-Guided Karma: When the Weather Memory finally breaks, Isaka's Living Connectors kill him from the inside out. Guess that's what he gets for dipping into Gaia Memory research a little too much...
- The Power of Love: Even Isaka himself was surprised to have grown to have actual feelings for Saeko, telling her that he wished to know more of the real her before his final fight against Ryu in #36.
- Power Born of Madness: The reason Isaka doesn't believe in the use of Drivers. Incidentally, he's the third strongest Dopant in the series and so completely insane that his own Memory couldn't make him worse.
- Serial Killer: Not only does he murder people to take their Gaia Memories, when he got the Weather Memory, he went on a series of murder sprees simply to test out his various elemental powers. Ryu's family are among his victims.
- The Starscream: Has offered to help Saeko overthrow her father and made good on his offer in "Beyond R". He failed.
- Superpower Lottery / Weather Manipulation: As the Weather Dopant, Isaka has nearly every Elemental Power in the book. It's not enough for him, though, and he continues to seek means of acquiring even more superpowers by devouring other Memories.
- You Killed My Father: Killed Ryu's entire family in cold blood. It creates one of Double's most powerful allies.
Mick Sonozaki/Smilodon Dopant
Portrayed by: Yasuhiro Takato (voice, Smilodon Dopant)Ryubee's (originally Raito's) pet British Shorthair cat. Also can become a Dopant through the use of the Smilodon Memory. The Smilodon Dopant can move into high speeds and can discharge electric currents.
- Defeat Means Friendship: You can even hear him purring. Justified, considering he was Raito's pet.
- Embodiment of Vice: Sloth, as befitting a lazy cat. Mick only acts on Ryubee's orders, and doesn't seem to particularly mind changing owners as long as he's fed and petted.
- Flat Character: There's not really anything to his character at all besides "is a cat" because, well, he's a cat.
- Mega Neko: As the Smilodon Dopant.
- Weaksauce Weakness: Waving objects in a certain way will make him stop a bit and expect food. Quite Pavlovian.note
A Dopant is created when a Gaia Memory is inserted into a human body, transforming the user and granting them supernatural powers. Each Gaia Memory contains the culminated knowledge of a single topic extracted from the True Gaia Memory; thus, Gaia Memories can be based on anything from the history of Earth, from natural phenomena to abstract concepts.
In normal cases, a human requires surgery before they can use a Gaia Memory. A Living Connector is imprinted upon the skin of the user, through which the Gaia Memory can be directly inserted into the body. While this maximises the power of the created Dopant, it carries a significant risk that the Gaia Memory will consume the sanity of the user and create a strong addiction to its power.
Gaia Drivers are external mounts that can be used to insert a Gaia Memory without surgery. While this limits the power of the Memory, it removes the negative side-effects. High-ranking members of the Museum equip first-generation Gaia Drivers to transform into Dopants, compensating for the power loss by using extremely powerful "golden" Gaia Memories.
Tropes embodied by the Dopants include:
- Attack Reflector: Jewel can do it with energy attacks.
- Badass Normal: Normally Dopants will go mad within a few days to weeks of using their Memory for the first time due to its addictive nature. The Beast Dopant managed to use his Memory for ten years without suffering any mental issues of note, not even Isaka's heightened megalomania. He's also one of the most powerful Dopants in the series in direct combat, with basically the same powers as Wolverine.
- Battle Couple:
- Beast and Zone are a husband-and-wife team who robbed an armored car ten years prior to the series.
- Magma and T-Rex were a couple who became Dopants together in order to take revenge on their former employer, but then T-Rex kills Magma when he becomes useless to her because he has been completely taken over by his Memory.
- Bitch in Sheep's Clothing: Several Dopants look kind and innocent until the truth comes out about their identities, which usually leads them to drop the act.
- Card-Carrying Villain: Quite a few Dopant abusers come complete with titles like Mr Question and the Radio Clown, sometimes with a one-shot Catchphrase or Bond One-Liner.
- Compelling Voice: Liar, who as the name implies, can literally make anyone believe anything, so long as it's not the absolute truth.
- Disproportionate Retribution: Quite a few Dopants use their powers for really petty reasons.
- Does This Remind You of Anything?: Gaia Memory use is paralleled with drug use.
- Elemental Powers: Magma, IceAge, and Energy.
- Old is pointed out by the characters to be one to Terror, given their "ancient" design and their use of a sort of sludge to attack. Old ends up acting as a trial run of sorts of how the characters intend to go about fighting Terror.
- IceAge and Triceratops are the first two Dopants Accel faces, compared to Magma and T-Rex, the first two onscreen Dopants Double takes on.
- The Masquerade Dopants could be seen as Expies of the classic Shocker Soldiers, given their skeletal design and status as easily-defeated Mooks.
- Fantastic Drug: Gaia Memories are highly addictive, grant a power high that often brings out the worst in the user's personality, and can wreak havoc on their mind and body with extended use.
- Genetic Engineering is the New Nuke: Gene, for his powers to work, needs biological material but can create anything from said material. For example, he created a plush cow on Shotaro's right hand with two leaves during their first fight.
- The Gunslinger: Arms.
- An Ice Person: IceAge.
- Invisibility: Invisible, though notably, Lily Shirogane didn't actually become a monster of any sort; Dr Isaka modified the Invisible Memory to allow her to use its power without such a change.
- It's Personal: Many of the Dopants. Notable are Puppeteer, who attacks the literary critics that panned the book he wrote in his daughter's memory; Magma and T-Rex, who wanted revenge on their old employer for firing them; and Yesterday, who turns out to be Kirihiko's sister and wants to get back at Saeko for her brother's death.
- Knight Templar: At their least twisted, Dopants end up as these. Triceratops and Commander are standout examples.
- Legacy Character: The final episode of the series establishes that multiples of the same Memories do exist; in this case, Anomalocaris and Cockroach. Another specific example would be Roidmude 077 becoming the next Beast Dopant.
- Love Makes You Crazy: Oh so much. T-Rex killed her lover Magma because he went crazy, Triceratops wishes to avenge her lover, Violence is Wakana's Stalker with a Crush, Nightmare is jealous to the point of putting his supposed rivals to sleep, Jewel set his unrequited crush up as the culprit though he was a monster to begin with. Commander is driven by a desire to avenge his dead wife, but unlike Triceratops, who on her own only wanted to kill those who caused his death, Commander decides to kill all criminals, regardless of crime.
- The award probably still goes to the Spider Dopant from the Kamen Rider Skull prequel in the "Movie Core War". Unable to live with unrequited love and having a well-hidden, but highly homicidal sense of jealousy, he gained the power to turn people into bombs, set off when a carrier touches someone they love, in a rather horrendous expression of If I Can't Have You . He ends up detonating a good part of the city in a single go, just to prove the lengths he's willing to go to make everyone as miserable as him.
- Made of Diamond: Jewel, quite literally.
- Magma Man: Magma, who else?
- Money Fetish: The Money Dopant.
- Monogender Monsters: Averted; people become Dopants regardless of gender. An even funnier detail to this aversion is that some of the more 'manly' Gaia Memories, likeT-Rex and Triceratops do in fact have female users.
- Mook Maker: The Commander Dopant can create Faceless Goons called Masked Soldiers out of thin air.
- Mythology Gag:
- One-Winged Angel: Certain Memories (particularly the ones based on animals) can make their user a larger Dopant, done in CGI.
- Quetzalcoatlus is this right of the bat, with no intermediate humanoid form ever seen (though this might be partly because the "user" was a parrot).
- Bird does this as a result of its Gaia Memory evolving.
- Commander upgrades his Gaia Memory to increase his power, changing form in the process.
- Overnight Age-Up: Old's specialty, at a price of about 10,000 yen for every year he ages the victim up. (Payment up front.)
- People Puppets: Puppeteer, though he mostly sticks with his dead daughter's Creepy Doll.
- Psycho for Hire: Cockroach and Old.
- Right Hand of Doom: Violence, whose left hand is an Epic Flail.
- Roaring Rampage of Revenge: Several are motivated solely by revenge.
- Shock and Awe: Energy in the finale.
- Small Name, Big Ego: The Sweets Dopant. She considered her restaurant to be "the best in Futo" despite the fact that it folded and closed in less than a year. Unfortunately, this lead to her snapping and using the Sweets Gaiamemory to kidnap and enslave Patissiers to be her personal source of sweets.
- Stock Dinosaurs: T-Rex and Triceratops.
- Stringy-Haired Ghost Girl: Virus can come very close, even though she's still alive (though in a coma).
- Super Speed: Cockroach, Smilodon, and Donburi.
- Sweet Tooth: Sweets, who sneaks desserts while working as a maid for the Sonozaki family.
- Teleport Spam: Zone.
- Two Guys and a Girl: Jewel and his friends. Him finding out that his two friends loved each other didn't go... well with him, which was very similar to Isamu Bitou and the Beast and Zone Dopants (he had no problems with them getting together, but still got screwed over for it).
- Voluntary Shapeshifting: Other than anyone with a Memory, Dummy can take on the appearance of anyone he wants, usually the dead to take advantage of the dead person's loved ones.
- Well-Intentioned Extremist:
- It seems to be this way with the original Cockroach, as he believed he was being a superhero.
- With Great Power Comes Great Insanity:
- Memories used without a Driver madden their user, and Drivers can be modified to mimic the effect of direct insertion.
- Using a Memory without the bio-port will cause grievous bodily harm and even death with extended use, as seen with the underage high school students who shared the Bird Memory.
- Yandere: Several of the Dopants are this trope, including the T-Rex Dopant, the Violence Dopant, and the Spider Dopant.
Portrayed by: Naoko KoudaA mysterious woman dressed in a black trenchcoat and oversized fedora, her face covered with sunglasses and bandages. Her main role in the series is as a supplier of gear, particularly to Ryu, Philip, and Isaka. She was later revealed to be Ryubee's wife and is exacting revenge for what happened to Raito/Philip.
- Bandaged Face: Caused by her husband, no less.
- The Chessmaster: Her opponent is Ryubee Sonozaki. Fitting the show's hardboiled theme, a billiards metaphor is used instead of chess.
- Childhood Friends: Movie Wars reveals that she's childhood friends with Sokichi, who helped her hide from Ryubee. In exchange, she made the Skull Memory for him.
- Embodiment of Vice: Wrath, the only thing Shroud has left.
- Evil Mentor: Shroud tries to be this to Terui, encouraging him to embrace The Power of Hate to become her weapon in her revenge against Ryubee. Eventually Terui rejects her mentorship and finds a better way.
- Evil Versus Evil: She's not much better than Ryubee, if at all, being directly responsible for the deaths of Accel's family.
- Gone Horribly Wrong: Giving Isaka the Weather Memory, although her warped sense of perspective means she's initially upset about it for all the wrong reasons.
- The Gunslinger: Her Shroud Magnum, a Palette Swap of the Skull Magnum. Comes with the Bomb Memory for a rather deadly Maximum Drive.
- HeelFace Turn: It takes until almost the very end, but Shroud is able to make peace with the last of the Sonozaki family. In so doing, she stops the unbeatable Wakana, saves Philip's life, and earns her happiness within the Earth's memory.
- It Was a Gift: All of Ryu's equipment, Double's Frog Pod and Denden Sensor, the vehicles and gadgets that Double inherited from Skull, Skull's own Memory, and Isaka's Weather Memory were all handed to them by Shroud to further her plans.
- Living on Borrowed Time: Shroud's sheer fury seems to have been the only thing keeping her alive after the injuries that led her to bandage her face. When she finally lets go of her hatred, she perishes soon after.
- Luke, I Am Your Father: She's Ryubee's wife and the mother of Saeko, Wakana, and Raito (Philip), whose face was burned by Terror's ooze after she refused to have Raito used as a Museum experiment.
- Nice Hat: As do most of the cast.
- Roaring Rampage of Revenge: Her motivation is getting revenge against Ryubee for taking Raito from her.
- Teleportation: Seems to have the ability to teleport objects in rings of fire as well as reappear and disappear. While an explanation for how she does this isn't given in the series proper, Word of God implies she's a Quark.
- Well-Intentioned Extremist: Few people have done so much evil in the name of good.
- Xanatos Speed Chess: The events of the entire series effectively amount to a game of Xanatos Speed Chess between her and Ryubee.
- You Have Failed Me: You no longer hate your opponent as much as you used to? Now you're useless to her, and she'll send you off to die.
Foundation X (unmarked spoilers)
- The Bus Came Back: After being absent from most of the later Heisei shows Foundation X finally returns in the Kamen Rider Brave special of all things.
- Evil Minions: Foundation X has their white-clad researchers.
- Evilutionary Biologist: They seem interested in artifacts which can further human evolution.
- Greater-Scope Villain: In addition to funding Museum and the Gaia Memories, Foundation X have been behind a number of other villainous factions as well.
- Katsumi Daido, the Big Bad of Double's summer movie, was originally a test subject of theirs who went crazy thanks to one of their researchers.
- While they don't appear at all in Kamen Rider OOO, the end of Double implies they had a hand in the research of the Core Medals.
- Foundation X reappear in Kamen Rider Fourze where they supported Gamou in his endeavors with the Zodiarts and The Movie depicts a business transaction between Gamou and one of their representatives.
- The villain of Kamen Rider × Kamen Rider Fourze & OOO: Movie War Mega Max is a rogue member of their organization, Lem Kannagai, and the first part of the movie deals with the Riders attempting to prevent a substance called SOLU from falling into Foundation X's hands.
- Kaisei Mogami, the Big Bad of Heisei Generations FINAL Build And Ex-Aid With Legendary Riders, is another rogue researcher of their organization (though his World of Build Alternate Self received funding from Namba Heavy Industries instead of Foundation X).
- In the special Kamen Rider Brave: ~Let's Survive! Revival of the Beast Rider Squad!~, a member of Foundation X appears as the ones behind the revival of Takeshi Asakura and the formation of the Beast Kamen Rider Squad.
- Mook Carryover: In Movie War Mega Max Foundation X employ the Mooks of dozens of other villain factions, including Masquerade Dopants, Waste Yummies and Stardust Ninja Dustards.
- Nebulous Evil Organization: A mysterious organization that backs the research of several other villainous groups.
- Ninja Pirate Zombie Robot: This is their hat as an organization whenever they take the active role as villain themselves. Nearly every member of Foundation X who actually takes on a combat form does so by combining at least two different power sources, and sometimes even more. They also have the ability to replicate the mooks and even the bosses of nearly every villainous organization from W onward, so their forces are often a chimera of various villain groups.
Jun Kazu/Utopia Dopant/Kamen Rider Eternal Red Flare
Portrayed by: Gong TeyuA representative of Foundation X, which researches Gaia Memories for the Museum. He rescues Saeko when she is attacked by the Smilodon Dopant and her Taboo Memory is destroyed, and reveals that he wants to help her overthrow Ryubee.
- The Blank: This is what he does to everyone associated with Philip in order to jumpstart the Gaia Impact.
- Broken Faceplate: The Utopia Dopant has this as part of its design, as an allegory to how a Utopia is a place that doesn't exist.
- Character Tics: Frequently becomes startled and drops things. Becomes a Brick Joke when you see how he inserts his Gaia Memory.
- Dead All Along: Killed by Katsumi/Kamen Rider Eternal in Eternal's V-Cinema, and was then taken back to the headquarters by subordinates, turning him into a Necro-Over.
- Energy Absorption: He literally sucked Accel's Super Mode right out of him, then used the energy to set him on fire.
- Even Evil Has Standards: Before his own atrocities occur in the series, he considered Dr. Prospect's "Heaven's Fall" brutal even by his standards during that time.
- Final Boss: He's the last major threat faced by Shotaro and Philip in the series.
- Iconic Item: His briefcase, which contains the T2 Gaia Memories.
- Light Is Not Good: A well groomed, impeccably dressed man clad in white who possesses the "Utopia" memory, which transforms him into an elegant gold Übermensch. On the other hand, utterly ruthless, calculating, and barely capable of expressing any emotion even before he died.
- Logical Weakness: Utopia's ability is to drain hope from its opponents and turn it into power, and is shown to be absolutely devastating when used against other living beings. However, this means that the ability is worse than useless against targets that have no concept of hope, such as mechanical automatons and inanimate objects. Shotaro manages to figure this out in time for the final battle, and deploys the memory gadget robots against Utopia to incredible effect, and even blocks the hope-draining ability with his hat.
- This is also a critical factor in Eternal's V-Cinema, where Utopia can't draw power from Katsumi, who's a zombie and therefore doesn't have any hope to draw from.
- Mind over Matter: The most commonly used of Utopia's powers. Turns out this is actually his own psychic power as a Quark.
- Ninja Pirate Zombie Robot: He's a Dopant, a Necro-Over, a Quark, and a former Kamen Rider as well.
- No Body Left Behind: After he's defeated, his body disintegrates.
- Not So Stoic: Calm and cold until he finally breaks down out of frustration at Saeko for not returning his feeling or appreciating his effort to make her "Queen" of The Museum.
- Power Floats: A variation: Kazu usually makes everything else float when he's about to use the Utopia Memory, or just showing off his psychic powers.
- Reality Warper: The Utopia Memory's power is granting the wishes of its user.
- Shut Up, Kirk!: His last words are a rebuttal of Double's Catchphrase.
- "You want me... to count my sins...? Then, is it a sin... to love...?"
- The Starscream: Appears to have offered to help both Sonozaki girls overthrow their father.
- Subordinate Excuse: Claims to have feelings for Saeko and thus wants to help her defeat her father. While Saeko is keen on defeating Ryubee, she finds Kazu repulsive enough to want to avoid his help.
- Too Spicy for Yog-Sothoth: How he is defeated. He uses his hope-draining ability on CycloneJokerXtreme, but ends up absorbing much more energy than he can handle.
Portrayed by: Maria Theresa GowJun Kazu's superior, a seemingly foreign woman in charge of the Foundation X front Charming Raven.
- Greater-Scope Villain: She seems to be a high-ranking member, if not the leader, of Foundation X and is the one who terminates Foundation X's research into Gaia Memories after Jun Kazu is defeated.
- Iconic Item: Her stopwatch.
- Schedule Fanatic: The moment her stopwatch beeps, it's off to the next task.
- Surprisingly Good English: Justified, as Maria Theresa Gow's father is Scottish and her mother was a Filipina. Of course, she still can't pronounce Museum.