Crossovers
- In the Quantum Leap/Star Trek: The Next Generation crossover All That Glitters
, when Sam leaps into Lieutenant Commander Data, Counsellor Deanna Troi realises that something has changed when she senses Sam’s emotions where Data should be incapable of feeling anything. Once she talks with Sam and establishes what has happened, Troi is able to offer Sam advice on how to pose as Data to the rest of the senior staff. Back in the past, Data is also given a full briefing on the nature of Project Quantum Leap, Al reasoning that there’s no concern about Data changing history given that he’s from the future and there’s no risk of him having any impact on the Project once he returns to his own time, to say nothing of him being able to offer vital aid in helping them work out what Sam might have been sent to the future to change. - Ruby is this for Noel and Penny in BlazBlue Alternative: Remnant, as she's the only other person who knows their nature as Murakumo Units and has promised them she'd help keep it hidden.
- Child of the Storm has Harry increasingly become this, partly because he's widely considered trustworthy, partly because he's thoroughly curious, and partly because he's pretty shrewd and good at deductive reasoning. By chapter 45 of the sequel, he knows that Bucky used to be the Winter Soldier, Carol is descended from Steve Rogers and Peggy Carter, Maddie is Jean's stolen at birth twin sister, Doctor Strange was originally known as Taliesin, Court Bard and Physician to King Arthur, and student of Merlin, that Hermione is actually the daughter of Wanda Maximoff and John Constantine, something that even Hermione herself doesn't know, the existence, name, and broad background of Clark Kent (particularly impressive, since his sole starting point was that Jean-Paul, a friend of his, had been in Kansas and being vague as to why, and that strange stuff happened in Smallville), and by implication, the identity of Draco Malfoy's mental hitch-hiker. And that's just the start.
- It becomes something of a plot point in the sequel, what with the nature of some of the secrets meaning that he really doesn't like having to lie — directly or by Exact Words — to some of his friends.
- Harry Potter and the Mystic Force:
- Snape, Sirius, and Tonks are the only ones to know where Harry escaped to after he's framed for faking the death of Cedric Diggory.
- Later, when Harry returns to Hogwarts in disguise, Luna recognizes him at once (somehow). Neville, Ginny, Fred, and George find out later when his disguise fails after he's exposed to a blast of raw magic during a fight. Later still, Draco Malfoy identifies him by his flying skills, playing Secret Secret-Keeper until he's finally pushed to confront Harry as Voldemort's actions escalate.
- Infinity Train: Blossoming Trail: While her status as the resident Nightmare Fetishist was known (and mocked) by her classmates, Chloe's aspirations of becoming a horror novelist was a secret to everyone but her younger brother, Parker, who constantly begged to read her short stories. Her father's lab assistants also turn out to have been aware that she at least writes such content for stress relief, but never told him because they didn't think the warning signs hidden within said works were all that important.
- Justice League of Equestria:
- Mare of Steel: The rest of the Mane Six, Princess Celestia, and Rainbow Dash's mother Firefly become this for Dash when she becomes Supermare. Thunderlane joins the list when he figures out her identity during her final fight with Brainiac.
- In one of the side stories, she and Batpony become this for each other when he deduces her identity, and she uses her X-Ray Vision to see that he's the real Prince Blueblood (who was kidnapped and replaced by Zod.
- Mare of Steel: The rest of the Mane Six, Princess Celestia, and Rainbow Dash's mother Firefly become this for Dash when she becomes Supermare. Thunderlane joins the list when he figures out her identity during her final fight with Brainiac.
- Kwami Magi Homura Magica has several beyond the canon ones across the multiple timelines the story mentions or explores.
- Rose joins Alya as one of Marinette's secret keepers in one of the earlier timelines Homura goes to Paris partially for health reasons. This Rose and Juleka had contracted with Kyubey, and following Juleka turning into a Witch and Rose, in revenge, tricked Monarch and Cat Noir to wipe out the Incubators, lost access to grief seeds and the Ladybug Miraculous became the only consistent source of Soul Gem purification left for her.
- In another timeline, this one being completely independent of Homura's actions, Marinette tells her parents that she's Ladybug following the defeat of Gabriel, giving her some more leeway in her actions as a result.
- Homura forces Gabriel's secret identity out of Felix in the main timeline the story follows, and a result of killing Gabriel and taking his Miraculouses gets attacked by Cat Noir, which leads her to discovering he's Adrien. She keeps both identities to herself out of respect for Cat Noir. As a result of seeing the above and other timelines thanks to Ultimate Madoka, Homura also finds out Marinette's identity, confirming it while the two are making a wish to drastically change reality to foil the Incubators and save Magical Girls, keeping the knowledge of it afterwards.
- In Kyon: Big Damn Hero, Rika and Kyon are this to each other, Miyoko/Miyokichi inadvertently became one, and Kyon's sister wants to become one.
- So far, quite a few members of the extended SOS Brigade trust Kyon's sister, but Kyon himself doesn't trust her.
- Last Child of Krypton: In the original story Shinji reveals his identity to Asuka. In the rewrite Fuyutsuki knows since the beginning. Asuka, Misato, and Ritsuko find out later and keep it a secret.
- In Lost in Camelot, as of Chapter 47, Arthur, Gwen, Lancelot, and Dyson are all aware (along with Gaius and Kenzi) of Bo, Merlin, and Morgana's status as beings of magic living in Camelot as a triad relationship.
- In The Magic of Torchwood, Jack and Ianto use the Fidelius Charm for two different secrets; Jack hides the location of him and his friends at Torchwood, and Ianto hides the secret of Jack's immortality.
- The Many Dates of Danny Fenton: Occasionally Danny has discovered the double lives of his dates and promises to keep their secret safe.
- Marvel Falls: Dipper and Mabel know of Kamala's identity as Ms Marvel and as the fic goes on, other people learn of it too.
- Soos in chapter 2.
- Lil' Gideon in chapter 4.
- Wendy in chapter 5.
- Doreen in chapter 6.
- Dante almost in chapter 7 then finally in chapter 10.
- Mermano in chapter 12.
- MLP Next Generation: Know Fear!: Sunny Skies is the first pony to find out Starburst's Secret Identity as the Fear Lantern, and agrees to stay quiet on it both out of respect to their friendship and because she feels she owes Star for saving her life in Stalliongrad. This ends up becoming a moot point when Starburst ends up outing herself as the Lantern while in her rush to save her mother.
- Origin Story: Many people think they know Superwoman's Secret Identity. She gets called "Karen Starr" all the time by various people. Thing is, Superwoman's real name isn't Karen Starr... it's Alexandra Harris. Alex's domestic partner Louise and the members of Runaways function as Alex's Secret Keepers.
- When he manages to guess the identity of Harry's father in Prince of Death, Chiron decides to keep it secret and recommends that Harry to do the same, fearing that the kid would be ostracized and subjected to murder attempts if it were known he's a son of Hades.
- SAPR: Celestia has a conversation with Ozpin using Sunset's magic journal, and she quickly pegs him as an immortal due to him being so Wise Beyond His Years. She promises not to tell Sunset or anyone else.
- In Say It Thrice, Lydia joins Sam, Tucker, and Jazz in agreeing to guard Danny's secret.
- Super Therapy!: Dr. Lynn Matthew knows most secret identities of her patients (not hard with Spider-Man considering he signs his checks with "Peter Parker"). Of course, she's tied up by doctor-patient confidentiality.
- Superwomen of Eva 2: Lone Heir of Krypton: Emil Hamilton to Asuka. Later, Kaji and Shinji learn she is Supergirl. Asuka also reveals her identity to Hikari.
- In The Weaver Option, Lankovar quickly identifies Gavreel as one of the Fallen but also determines he is a Loyalist. Given the Dark Angel Successor chapters would kill Gavreel regardless of his loyalty, Lankovar keeps the secret and helps arrange a cover identity.
- Wonderful (Mazinja): Before Wonder Red revealed her existence to the world and her Secret Identity to the PRT, Emma and Sophia knew that she was Taylor Hebert.
- All Assorted Animorphs AUs: In "What if Rachel's mom was a controller?", after Rachel tells Jordan and Sara the truth about the Yeerk invasion, Jordan in particular often helps to cover for her with Naomi.
- The Sword Shall Devour: Caitlyn hides in the Undercity to escape the Noxians' purge of the Piltovan aristocracy, effectively being adopted by Vander. While the fact that she's a Piltie is no secret, only Vander and Vi know that she's the Kiramman heir.
- In The Cutting Edge, Ra's al Ghul becomes the first person Laurel tells about her affiliation with Mar Novu. However, Laurel only later tells Sara that she's from the future, letting others assume she's "just" Mar Novu's chosen warrior.
- In Angel of the Bat, after the final battle, Monsignor Ryan sees Angel without her mask on. As he sees her in a confessionary, he cannot tell anyone else what he now knows... Not that Ryan appears to be the sort to do so anyway.
- Dance with the Demons:
- Dr. Douglas Dundee, the physician who delivered Bruce Wayne, knows Bruce's Batman "because he had to patch him up so often".
- James Gordon knows his daughter is Batgirl, but he's unaware of Batman's true identity (which Barbara knows, of course)."I'm going to try to hook up with some of the others," she said. Gordon had learned years ago that his daughter was Batgirl, but the Batman's true identity was a mystery to him.
- The original BSG fanfic, Flights of Angels has Boomer being the only person in the Fleet who knows Apollo and Starbuck are having an affair until the ending where their love is revealed.
- In Code Geass: The Prepared Rebellion, Milly and her grandfather are two of the very few people who know Lelouch is Zero.
- In Class 78th Watches the Future, before it's revealed as Class 78 watch their future, Makoto, Leon, and Mondo were all aware that Chihiro Fujisaki was actually a boy.
- In Danganronpa: A New Horizon of Despair, Tarou promises to be this for Shin, who doesn't want anyone else to know his Ultimate talent.
- Facing the Future Series:
- The author feels that everyone at the South Pole who learned Danny's secret at the end of "Phantom Planet" became this, believing there were bigger secrets than what a fifteen-year-old boy did in his spare time.
- As of Ancient History, Tanya.
- In Hope for the Heartless (which takes place shortly after the events of The Black Cauldron), the resurrected Horned King imprisons a peasant girl named Avalina — who stumbles upon his castle during one stormy night — to keep his return a secret from Prydain. He threatens to kill her and her loved ones should she try to escape, but grants her request to say the proper farewells to her family. During her short stay with her mother and brother, she asks them to keep everything a secret to prevent mass panic from erupting due to the Horned King's resurrection. They eventually agree reluctantly, realizing that they can't possibly do anything without potentially endangering Avalina's life.
- Months later (with the Horned King and Avalina having grown closer during that time), the lich and the girl stumble by chance upon Taran the pig-keeper and Princess Eilonwy (who are Avalina's friends) while being outdoors. The vengeful lich almost kills them, but Avalina manages to change his mind and they depart. Taran and Eilonwy tell of this encounter to Dallben. After gaining confirmation from Hen Wen about Avalina's account of the events leading there, the trio decides to remain silent for the same reasons as Avalina's family.
- After the protagonist of Never Been Bothered learns that Elsa and Anna are secretly sisters, they promise not to tell anyone. It helps that they suspected they were siblings as they look too similar to be unrelated somehow.
- In All This Sh*t is Twice as Weird, Victoria becomes this with regard to Cullen's Dark and Troubled Past as a young Templar. The other Inquisition leaders know that he's deeply troubled by the way the Orlesians treated him at the Halamshiral ball, but she's the only one who knows why. (It's implied that Cole also knows, but he won't speak of it to anyone but her.)
- In the first installment of Skyhold Academy Yearbook, Varric is this for Hawke regarding the real reason she's taken sabbatical from the eponymous school. Later, Cassandra takes on the role for Varric, after she accidentally stumbles across both the secret he's keeping for Hawke and the one he's keeping for himself.
- In Just Add Water (Akela_Victoire), Camilo is the first person to find out about Mirabel's gift and agrees to keep it a secret.
- When Anná discovers that Bruno was hiding in the Casita's walls the whole time in La polilla y la mariposa, she is understandably upset with him before becoming this, helping him mend the cracks in the house years before Mirabel finds them.
- Two butterflies: gone with the wind.: Instead of kidnapping his niece, Bruno goes to Julieta and explains that Mirabel will be miserable in the future if she stays in Casita, and with her blessing and help he takes Mirabel away. Julieta then plays along when Alma informs her that her daughter and brother are missing.
- In The Two Seers, Dolores figures out that her uncle and cousin were living in the walls and ends up becoming a secret provider for the both of them. When Camilio has a run-in with Mirabel, Dolores refuses to say anything about it to him.
- Girlfrenemies: Raven accidentally blabs to Maddie and Dexter that her relationship with Apple is a lie to make royals and rebels get along. They agree not to tell anyone.
- Springtrap and Deliah: Harry finds out about Springtrap's past murders when Springtrap tell him to try and discourage him from making friends with Deliah. He records their conversation on his phone and threatens to make it public if Springtrap doesn't back off. He does keep it to himself when Springtrap asks him too, under the condition that he tell Deliah himself at the end of the summer. In the Light Ending, Springtrap fesses up as promised.
- In Little Miss Heropants, Lilac has PTSD from Lord Brevon torturing her and Carol has to keep this a secret, especially from Milla.
- InThe One With the Butterfly Effect, Rachel becomes this for Monica and Chandler's relationship instead of Joey. However, she's only keeping the secret from Ross, Joey, and Phoebe, to the extent that she admits that she told some of her work colleagues about the relationship, justifying herself on the grounds that her work friends don't know Chandler and Monica and won't care that much about it.
- Elemental Chess Trilogy: It is revealed that Maes Hughes was this for Roy Mustang and Riza Hawkeye, before and during the early part of the canon. Hughes, who was Mustang's best friend, was the only one who had absolute confirmation of the actual Secret Relationship between the two (though plenty of other people guessed).
- Kimberly T's Gargoyles:
- While most of Xanatos's personal staff know about the gargoyles, only Anne Marsden knows about Alexander's magical potential and Owen's true nature as Puck.
- Vinnie, the human who has had irregular run-ins with the Manhattan Clan, meets Demona while assisting the Japanese clan during their visit to New York, and becomes one for her when he learns about her human identity. He is subsequently given a job at Nightstone Enterprises as thanks for keeping the secret and as compensation for the losses he has suffered due to the Gargoyles.
- Daphne Greengrass and the Boy Who Lived:
- Daphne basically becomes this for Snape, as he insists that she not tell anyone about his deeper reasons for certain actions in Harry’s defence, up to Daphne learning about Snape's past with Harry's mother. She muses at one point that this is the only secret she's truly keeping to herself, and only because others knowing it would put Snape's safety at risk.
- A minor example when Daphne tells Tracey Davis how Lily's sacrifice saved Harry from Voldemort in the first place; she concedes that it's not that big a secret when Voldemort already knows it, but asks that Tracey not share that detail where Draco Malfoy might overhear it.
- Talking with Bill, Daphne learns that Secret-Keepers are generally discouraged from living in a property that they are keeping secret as their presence will cause the charm to decay, which justifies why James and Lily had someone else be their Secret Keeper rather than do it themselves. Bill is able to be the Secret-Keeper for himself and Fleur as they live at Nest Cottage as the charm will still protect them for just over a year, Bill reasoning that by that point either Voldemort will be defeated or they'll have to flee the country.
- In My Brother, before Harry starts at Hogwarts, only a few people are aware of the existence of Emma Lily Potter, Harry's little sister, born while the Potters were in hiding just two months before Voldemort killed James and Lily. Aside from the Marauders, Dumbledore, McGonagall, and Hagrid, the only others who knew about Emma were Bathilda Bagshot who lived in the area, and Amelia Bones and Bartemius Crouch as they were the department heads who helped hide Emma in the first place. Ron and Hermione are the first students at Hogwarts to learn that Emma exists, followed by the rest of the Weasleys, before the rest of Hogwarts learns of Emma's existence at the Sorting.
- In The Power of Seven, Demelza Robbins is chosen as the secret keeper for Harry's 'harem' of girls (Ginny, Hermione, Luna, Demelza, Susan Bones, Katie Bell, and Fleur Delacour) because she's the least obvious choice as the apparent "weakest" of the girls even as they all trust her loyalty.
- Becoming Lífþrasir: During Hiccup's time as "Cattongue", only a few people knew who he really was, including Thuggory, Heather and Camicazi. Eventually Gobber catches him without his mask on in his old study at the forge and agrees to keep his secret, and Fishlegs and Astrid work it out on their own a few days later.
- Dark Valkyrie: The few people who see the slave brand on Hiccup are determined that no else finds out, since Hiccup could lose his status as heir if he did. His friends end up finding out anyway, and are determined to help him through it. They even come up with a plan to give him and themselves a tattoo to cover it up and make it less likely that anyone will figure it out.
- By the time Hiccup returns to Berk in Prodigal Son, Astrid and Fishlegs already knew who he was.
- In If I Could Start Again, outside of his parents, Loki, Sif and the Warriors Three, Hawkeye and Black Widow are the first non-Asgardians Thor has told about his experiences in an alternate future timeline. The agents share that detail with Fury and Maria Hill to help them make plans against Hydra, and later the Ancient One reveals that she is also aware of Thor's status as a time-traveller through her experience of the Time Stone. Thor's meeting with the Ancient One also leads to Brunhilde and Kaecilius learning about the time-travel factor.
- Peta Parker: For a while, Deadpool and Vanessa were the only ones who knew the truth behind "Spider-Man".
- When Peta sensed the bomb about to go off, she was forced to reveal herself to be Morgan's favorite superhero when she saved her.
- In Z To A, out of all of the Avengers, the time-displaced Peter and Wanda only tell Steve Rogers the truth about exactly when in the future they come from before Thanos is defeated (they only tell Fury enough to confirm that they know about Carol), otherwise letting everyone think they were sent back with memories of everything up to the Snap and meeting each other in the afterlife dimension of the Soul Stone.
- In the Self-Insert series Mass Vexations, Tali eventually becomes Art's secret keeper.
- He gets a lot more secret keepers in the sequel: as of the moment, Garrus, Madison, Thane, Kasumi, and Shala'Raan have all found out.
- In Mega Man: Defender of the Human Race, ProtoMan is this for the fact that Nomad's alive.
- Cut Man, Guts Man, and Magnet Man are this for ProtoMan meeting with Nomad.
- Back To Us: In Chapter 24, Alya becomes one to Adrien after she runs into him when he's about to transform into Chat Noir.
- Leave for Mendeleiev:
- The concept is completely Defied by Adrien, who has absolutely no respect for the concept of The Masquerade. His sense of entitlement towards his partner extends towards her Secret Identity; no matter how many times Ladybug rejects his unwanted advances or reminds him that they need to remain unaware of each other's civilian identities for safety's sake, he continues doggedly pursuing any clues.
- When Lady Wifi "exposes" Chloé as Ladybug, Adrien not only believes it, he gleefully mocks his partner, casually addressing Ladybug as Chloé and offering to reveal himself to her as well. When she ducks into a closet to detransform, he camps out in front of it while complaining about how she shouldn't bother trying to hide anymore. It takes seeing Chloé outside while he knows Ladybug is still trapped inside for him to realize his mistake... and fixate on why everybody thinks Chloé would make a horrible hero.
- This turns Adrien into a Spanner in the Works for Lila when she "confides" in him, falsely claiming to be the Fox Heroine Volpina. Despite her asking him to keep this secret, Chat Noir casually outs her while she's being held hostage by an akuma, cementing just how little he respects the concept of secret identities and how little he cares for her safety. Lila is left with a serious grudge against Chat Noir for his carelessness, as well as against Adrien for having Loose Lips, though she remains unaware that they're the same person.
- Near the climax of the story, Adrien appears to have learned from his mistakes, as he witnesses Ladybug entrusting somebody with a temporary Miraculous and doesn't immediately out them. Sadly, he soon proves that he just doesn't get it when he complains to his father Gabriel, once again casually exposing their identity... as well as unintentionally revealing that he WAS Chat Noir as well. Gabriel then hits him with a blistering "The Reason You Suck" Speech, noting how Ladybug likely has good reason not to trust him.
- Heroes in The Legend of Royal Blue and La Sylphide aren't as adept at hiding their identities. Emilie's Old Retainer Simone recognizes La Sylphide after hearing her voice, and Gabriel detransforms in his room before seeing his classmate Julien Bonheur had let himself in. The two of them are glad to provide alibis and moral support when needed, and sharing the secret helps Gabriel and Julien develop a real friendship.
- One of the biggest changes in Miraculous! Rewrite is that the heroes are permitted to select somebody to serve as their official confidant, allowing them to reveal their Secret Identity to them. Marinette chooses Alya as hers; Adrien picks Nino.
- Recommencer:
- Principal Achthoven knows about the Miraculi, recognizing Marinette as the current Ladybug. After privately revealing this to her, she helps provide cover for her Secret Identity. Later on, she becomes one for Madame Red and Qashr-Tari as well, having recognized them, and after confronting Master Fu, selects a new Ox hero.
- After Adrien is given the Bee Comb, they contact Chloé in a panic, since her former identity as Queen Bee is well known. This naturally means that they're aware of Amellié's secret identity, which eventually leads to her learning that he used to be Chat Noir.
- Played With through Alya. Lila falsely confides in her that she's Imperatrix, in order to leech off the new heroine's fame. This comes back to bite her when Alya publicly accuses the real Imperatrix of being a fake, as that's the only way she can reconcile Imperatrix showing up while Lila's around.
- In Spotless, Kagami finds out that Marinette is Ladybug when she detransforms in front of her, not noticing Kagami in her room when she returned from a battle. Naturally, Kagami is quick to fret and worry over Marinette being in danger.
- Two Letters:
- The first of the titular letters was sent to Luka and opened with Marinette confessing her Secret Identity to him, as well as admitting that she was tired of being Ladybug and wanted out.
- As his status as a former temporary hero has been exposed, Luka has to deal with Mayor Bourgois harassing him over rumors that he might know who the original Ladybug is. The Mayor also tries extracting the secret from Marinette after recalling that she was once Multimouse, unaware that she's the very person he's looking for.
- One of the reasons why Marinette is so furious with Alya is because of how blithely she treated her own secrets. As she explains, she'd spent a year and a half bearing the burden of being Ladybug alone before she finally cracked under the pressure and shared her secret identity with Alya, hoping that she could trust her to become her confidant. Alya, by contrast, barely lasted two weeks before she let Nino know that she was Rena Furtive, completely ignoring how this endangered not just her, but Marinette by proxy.
- Nino in Won't Tell a Soul serves this to Marinette/Ladybug and later to Adrien/Cat Noir.
- Entropy: The Fate of the Hero System: Deconstructed in Kota's Hero Academia: The Rise of the Ultimate Villain, as Midoriya still hasn't told anyone about how Todoroki revealed his father's abusive nature to him during their first Sports Festival. When the Fallen Heroes Alliance finds some old security footage capturing the confession, they post it online, leading to public backlash against Izuku for keeping his silence for years. Though his fans point out that nobody would've believed him, Izuku himself admits it was a mistake and apologizes.
My Little Pony: Friendship Is Magic
- A Brief History of Equestria: Prior to the birth of Pansy's son Plow Blade, the only pony who knew about her relationship with the Earth Pony Trencher was her friend Shield Skin, who they even used as a secret messenger. This lasted for years, until Plow Blade's birth — since he was an Earth Pony like his father, Pansy was forced to admit the truth, leading to Hurricane trying to arrest and kill Trencher, which kicked off the Winter War.
- The Elements of Harmony and the Savior of Worlds: Celestia and King Spykoran are the only ones aware that Spike is Spykoran's long-lost grandson. They agree to keep the secret for the time being, because they can tell he's quite happy with Twilight.
- A Hairier Problem: Rise of the Furball: The Cutie Mark Crusaders initially become this for Apple Bloom when they witness her first transformation into a werewolf. Babs Seed later is introduced to the secret after accidentally witnessing it herself, and Silver Spoon has to keep it as well following her Heel–Face Turn. The other new lycanthrope, Lightning Dust, has keepers in Rainbow Dash, Applejack, Fluttershy, and Twilight, but thanks to a slip-up by Rainbow on Nightmare Night Rarity, Pinkie Pie, and Spike learn her secret as well.
- The MLP Loops: Changelings (usually) have a Hive Mind, so in loops where their Hive Queen Chrysalis is Awake, the entire hive is aware of the looping nature of reality. They keep quiet about it, and are notably very respectful to the loopers, who they know are infinitely older and more powerful than any of them.
- A Growing Affection:
- The five Kages and the leaders of three Kekkei Genkai clans (one of which is Hiashi, the other two are unrevealed) hold the secret origins of bloodline traits.
- Tsunade and Jiraiya, with Kakashi and Shizune as backup, keep the secret of Naruto's father's identity.
- Guilt of Innocence: The only people who know about Sasuke's mission as a mole in Otogakure are Kakashi, Tsunade, and Jiraiya. Kakashi because he is the only adult in Sasuke's life on account of being his sensei, Tsunade because she's the Hokage and the one who came up with the idea, and Jiraiya because he is Konoha's spymaster so it would be counterproductive to hold the information from him.
- in dreams you follow (but I dream in the dark): The only ones aware that Kiba is a Fake Defector are Tsunade and Genma. Tsunade was the one who agreed to send him on this mission, while Genma gave him a crash course in poisoning techniques.
- Naru-Hina Chronicles: After learning that Shikamaru and Temari are dating, Naruto promises them to not tell anyone about it. Eventually, everyone else finds out about it (with Gaara figuring it out on his own while Ino and Choji learn about it upon seeing Shikamaru and Temari kiss each other).
- Three's A Crowd: Over time, Shikamaru, Ino, and Chouji learn about how Sakura has been secretly studying overtime and teaching herself things they haven't learned at the Academy. Shikaku and Yoshino later catch her practicing her own spin on Sunan puppetry techniques and encourage the kids to ensure they keep this hidden, as they don't want her attracting undue interest.
- The Child of Love: At the beginning, very few people know Asuka is pregnant (Shinji, Misato, Rei, Ritsuko, Gendo, Fuyutsuki, Hikari) and they keep it secret.
- Doing It Right This Time: Sakura and Nozomi know about her brother and her middle sister (respectively) and other people being time-travelers and are keeping it secret... despite Sakura being very loud and indiscreet.
- In Once More With Feeling (Crazy-88), Kaji is the only major character who knows that Shinji's a time traveller.
- In Time Fixers: Nicktoons of the Future when Max reveals that he is a genius like his parents, SpongeTron promises him that he will keep it a secret from everyone else.
- Second Wind: The only ones who know that Luffy and Zoro are time-travelers are people that they consider family.
- In Chapter 24, they tell Ace, who may later have informed Sabo offscreen.
- In Chapter 26, Luffy and Zoro agree to let Ace inform Whitebeard of it.
- In Chapter 54, Luffy tells Garp, who privately swears to take the knowledge to his grave. Immediately afterward comes The Reveal to the rest of the Straw Hats.
- Brook, the only one not present for The Reveal, finds out at the end of Chapter 60.
- In Chapter 62, Luffy informs Rayleigh and co., who then reveals the true history of the Roger Pirates to the crew in turn.
- This Bites!:
- Prior to The Reveal in Chapter 14, Soundbite was the only one who knew that Cross knew a lot more than he was letting on, but even he didn't know everything; it seems that somehow his knowledge from the Internet doesn't extend to One Piece itself.
- Post-Reveal, the crew keeps his secret; the outsiders that have learned the truth about Cross thus far are Ace, Vivi's family, Iceburg, Paulie, Zambai, Dragon, Koala, and the New World Masons.
- Zoro and Nami also serve as this; whenever there's sensitive information that needs to be handled properly, Cross shares it only with the first and second mate… and Soundbite, of course. Though in Chapter 24, as part of penance towards Vivi, Cross agrees to let her in on it as well, and in Chapter 43, Merry comes in as well, having technically been a part of it all along. He formally adds Robin (who had been not-so-subtly eavesdropping the whole time) in Chapter 59.
- In Chapter 28, Cross writes down all of his relevant knowledge for the Skypiea arc, knowing that he won't be able to speak freely while Enel is around. He asks Robin to help him out because she's the one with experience in being discreet when one slip-up could mean death because her powers will help him write faster...and because she'd just use said powers to peek at his notes anyway.
- When the Marine training grounds were moved to Navarone, Jonathan ended up telling Instructor Zephyr about their endeavors to bring down the Government, asking him to be a member. Though Zephyr closes off when he hears they're getting intel from pirates, he is sympathetic enough to their cause to keep their secret.
- Lassoo and Funkfreed become this to Soundbite after the snail tells him what he witnessed: that both Zoro and Nami find their dreams less worthy than Luffy's and Cross's, and that if they knew, the conflict would tear the crew apart.
- Garp promises to keep the secret that Perona, the newest Warlord of the Sea, is actually a close ally of the Straw Hat Pirates.
- Learning How to Be a Princess: Luz being the daughter of Emperor Belos is meant to be a closely-held secret initially only known amongst the Emperor's Coven and a small number of the coven heads until her coronation. Thanks to both her inability to keep a secret and just bad circumstance, several characters end up learning ahead of time, but most of them thankfully become this trope: Amity because she feels bad watching Luz panic after absent-mindedly introducing herself as Luz Noceda-Belos; Eda and King because they like Luz and also to remain on her dad's good side; Willow and Gus because they've already been good friends with Luz for a while; and Amity's parents because Luz outright threatens them with her father's wrath.
- Persona 4 SILVER BLUE: During the fight against Shadow Yosuke and Shadow Labrys, both Yosuke and Teddie learn the truth about Labrys's past and they both swear to keep it a secret. At the time of this writing, they're the only members of the Investigation Team who know about Labrys's true nature.
- In Pokémon Reset Bloodlines, outside of his Pokémon, Ash has only shared his secret about the collapse in reality and the creation of the new timeline with Mewtwo and Casey Snagem. Sabrina also knows it, having figured it out herself by reading his mind without his knowledge, but doesn't seem interested in using it against him.
- Travels of the Trifecta: There are two secrets being kept by both Paul and Conway after the two of them part ways in Chapter 10, and each of them has at least one Secret Keeper. Candice and the Nurse Joy from Snowpoint City are the two people who know that Paul is terminally ill, and Maylene is the only person who knows that Conway is still alive and didn't die when he fell out of the helicopter.
- A Force of Four: Andrew Vinson knows his lover Karen Starr is Power Girl's secret identity.
- Hellsister Trilogy: Fred and Edna Danvers know their daughter Linda is Supergirl, and they also know Clark Kent's real identity. Fred thinks he is able to guess Batman's identity since he met him once, but Linda warns her father against getting too nosy.Fred Danvers: I never thought he'd finally do it, Linda. But tell me something, will you?
Linda Danvers: What's that, Dad?
Fred Danvers: I know who he is. And I know who you are. But are some of these guys and ladies around here, maybe, well—part of the team?
Linda Danvers: (innocently) What team is that, Dad?
Fred Danvers: You know what team. It'd be really fun if you took me up to shake hands with some of them. Now, it's not like I want to know which ones they are. But you know, I have met the Gotham guy. And I'll bet I could guess which one he is, if I tried. Is it kind of like the Mafia? Do you say, 'This is a friend of mine'?
Linda Danvers: Dad, I've gotta tell you. Whenever we think somebody's getting too curious, we have to take him to the guy from Coast City. And the Coast City guy has to use that thing on his finger to go over your mind like a Disk Doctor over a hard drive, and purge out those curiosity bumps. After it was done, you wouldn't even remember everyone that was here.
Fred Danvers: Hmph. You guys used to have to go through such stupid stunts to keep your secrets secret.
Linda Danvers: That was before we met the guy from Coast City. - In Kara of Rokyn, Lois becomes Superman's secret keeper before their wedding.
- Children of Remnant: Qrow and Clover clearly recognize Neopolitan on her date with Emerald but decide to let them be for the sake of not causing a scene.
- In A New Order, Naru and Rei's Grandfather know Usagi and Rei are Sailor Moon and Mars, respectively.
- Naru from Sailor Moon becomes this in any fanfic where she finds out Usagi is Sailor Moon. Examples include Sailor Moon Z and Beautiful Destroyer Sailor Moon.
- Queens of Mewni:
- One of the biggest secrets perpetuated by Luna the Child is that her mother was Eclipsa, Queen of Darkness, whom Luna did everything she could-including casting a spell on the entire Mewnian population-to erase from living memory. To that end, she rewrote the Book of Spells and presented the fake book as the real one. The only ones that knew the truth were Luna herself, Glossaryck, the Magic High Commission, and Sky the Weaver, who had found the real book while trying to find a way to repair the fake one. When Star found out the truth, she had a Heroic BSoD of epic proportions when she found out everything she had done was Based on a Great Big Lie.
- The only two people that knew Celena the Shy's shyness was (mostly) Obfuscating Stupidity were Celena herself and Glossaryck, who saw through the act.
- In Eros Turannos, after Padme learns that she's pregnant, the only other person aware of this discovery is Shmi, as she wants to ensure Anakin stays focused on the upcoming confrontation with Palpatine until the Emperor is dead.
- In My Mother, after Padme is discovered frozen in carbonite, Luke and Leia are surprised to learn that Artoo has known so many details about their family history, to the extent that he still has the recording of Anakin and Padme’s wedding.
- In Padawan's Return, when Ahsoka Tano from the time of the Empire finds herself in the past during the events of The Phantom Menace, the only two people she tells her true identity and origin are R2-D2 and Plo Koon, as she needed Artoo's help to establish a cover story and Plo's bond with her younger self meant that he could tell she wasn't just a Tortuga who shared the same name.
- Supergirl (2015) fanfic my youth is yours: In college before they started dating, Lena was the first person Kara ever told about her alien nature. When Lena heard a new Kryptonian had saved a plane, she put two and two together before she even saw the pictures of Supergirl.
- The Wizard and the Huntress:
- Having known Jim since they were little, Toby has been this for Jim, Douxie, and Barbara's status as wizards, becoming the Token Human for their nightly excursions.
- When Claire becomes the Trollhunter, Mary and Darci become this for her.
- Predator and Prey: Geoff, Noah, Leshawna, Gwen, Trent, Justin, and Heather are the only people who know that Bridgette was sexually abused and raped by Alejandro during Total Drama World Tour, and they have all agreed with her to not reveal this to anyone to protect Bridgette. As a result, Alejandro is still merely seen as a Faux Affably Evil Manipulative Bastard by the show and everyone else rather than the incredibly depraved sexual predator he is off-camera and in reality.
- In Black Crayons, not including those connected to the government or NEST, those who know the truth about the Cybertronians include Sam, Mikaela, Annabelle, their families, and Leo (though he hasn't appeared in the series).
- Where We Don't Belong: Mio agrees to keep Nia's status as a Flesh Eater. She finds out after Nia reveals it to heal Mio, Sena, and Nimue after their encounter with Teach and Miyabi.
