Alice and Bob have always been best friends. Maybe they're even developing feelings for each other. The trouble is, Alice has supernatural powers, and Bob doesn't. And for some reason, she can't tell him about it.
Maybe Alice moonlights as a superhero, and she doesn't want anyone to find out about her Secret Identity. Maybe she's a witch, or some type of supernatural creature, and she's afraid of persecution. Or maybe the Masquerade keeps her from telling anyone else about her predicament, with dire consequences for rule-breakers. Regardless, the protagonist is forced to hide their true identity from the people around them, especially their best friend.
Such cases often go through the struggles of the protagonist to hide their true nature. If Played for Laughs, the characters may unwittingly riff on this (if Alice is a vampire, for example, there may be ironic quips about how she's acting "dead" or how a situation "bites"). The plot often leads up to an inevitable Internal Reveal where the protagonist's friend is let in on the secret. Sometimes it's intentionally exposed to them as a test of friendship, with the friend becoming a Secret-Keeper. In other cases, the friend discovers it on their own and decides to continue playing dumb. However, it's also fairly common for Status Quo Is God to be in effect, with the friend remains unwitting throughout the entire story or series.
- Bleach: Tatsuki and Ichigo were very close as children and shared everything except one thing; when Tatsuki asks if it's true Ichigo can see ghosts, Ichigo lies and says he can't. Later in life, Ichigo becomes a shinigami and Tatsuki gains the ability to see ghosts. Not only does Ichigo hide his shinigami activities from her, she hides the fact she knows about them and that she can see ghosts.
- Kotarou Nomura in Digimon Ghost Game is the Beady-Eyed Loser friend of The Leader Hiro, but despite not being a Digimon Tamer or even aware of their existence, somehow he ends up being preyed upon by the Monster of the Week in every single one of his appearances.
- Subverted in Kyo Kara Maoh!, in which Murata is a picture-perfect example of this trope, complete with unsuspectingly dragging Yuuri into situations where he just happens to fall into water and get dragged to the other world...until it turns out he was, in fact, in on it and facilitating all along, and knows considerably more about what's happening than Yuuri does.
- In Magical Girl Lyrical Nanoha A's, Dr. Sachie Ishida, Hayate's treating physician, is pretty much the last muggle adult kept out of the loop (that Hayate, Nanoha, etc. are magic-users). Leads to an amusing conversation in one Sound Stage, where the mages are supposed to mind their tongue around Ishida but fail repeatedly, such as when Signum is unable to bring herself to address Lindy as anything but "Admiral".
- In Puella Magi Madoka Magica, this gets deconstructed with Sayaka's friend Hitomi, unaware that Sayaka was a Magical Girl. When Hitomi tells Sayaka that she's going to confess to their mutual crush Kamijo the next day, unless Sayaka does it first, she is unaware that Sayaka was being pushed closer to the edge, having already begun a Break the Cutie process of learning just what being a magical girl meant in this world and putting her 'hero of justice' ideals too high to actually achieve, with the final result being that Sayaka turns into a witch. The sequel manga does have a scene of Hitomi admitting to feeling immense guilt over Sayaka's disappearance as Madoka's wish results in magical girls simply disappearing instead of turning into witches, knowing that her ultimatum was likely the breaking point.
- An inversion occurs in Rosario + Vampire. Tsukune is the token human who tries to keep his humanity a secret from his friends. They're pretty blind to it for most of the first season. Eventually everyone finds out, but he manages to convince the majority of the school he isn't human. And then eventually it ceases to be an issue because Tsukune ceases to be entirely human.
- Naru/Molly plays this for Usagi in Sailor Moon... at least up to the point where she gets Demoted to Extra.
- Spider-Man keeps his identity a secret from everyone he knows; friends, colleagues, even his Aunt May. Mary Jane was the only one he let in on the secret.
- The title character is a super powered alien from another planet who disguises himself as mild mannered reporter, Clark Kent. His friend Jimmy Olson doesn't know the truth and neither do any of his co-workers. Lois Lane might or might not know Depending on the Writer. The only other muggles in on the truth are Superman's adoptive parents who may or may not be dead, and Lana Lang DOTW.
- This is played with in All-Star Superman, where Lois is the unwitting muggle friend and Jimmy is a (possibly secret) Secret-Keeper.
- Shang-Chi and the Legend of the Ten Rings has Katy as Shang-Chi's muggle friend. He kept her in the dark about his identity for ten years and would have kept it that way if not for Razor Fist and a bunch of Ten Rings members attacking him on their bus to work.
- All four aliens in 3rd Rock from the Sun had friends and even love interests who didn't know the truth about them.
- Iris is this to Barry in the first season of The Flash, until she figures it out towards the end. She’s rather pissed to find out that her best friend, boyfriend, and father were all keeping her Locked Out of the Loop.
- Supergirl: Lena is Kara's best friend, but she has no idea that she is Supergirl until the tail end of season 4. She doesn't take it well.
- Foggy spends most of the first season of Daredevil (2015) ignorant of Matt's crimefighting exploits. When he learns about it, he is pissed.
- Forever: Jo and Henry become close friends, but until the very end of the series, she has no idea Henry is immortal. Lucas also might qualify by the end of the series, having been let into Henry's basement laboratory among other things but still not knowing Henry is anything beyond an exceptional man.
- In Forever Knight everyone else on the police force generally, and Nick's partners Schanke and Vetter in particular, are unaware that he's a vampire. In a twist, Vetter is aware that there are vampires but she thinks that she's keeping that a secret from him.
- Both Hank and Juliette on Grimm are clueless about Wesen and Grimms, at least in season 1.
- Henry Danger: Charlotte and Jasper were this to Henry's identity as Kid Danger for the first two seasons. Charlotte finds out early on in the fourth episode of the first season, while Jasper finds out in the Season 2 finale.
- Lucifer: The titular character's mortal friends are all this, as nobody believes his claim of being the Devil. The twist is that Lucifer never tries to hide his identity, as he never lies, after all. It's just that with him being the owner of a luxurious nightclub in Los Angeles, where practically everyone can create a persona to make it big, claiming yourself as the Devil is kind of a cliche. This gradually dissipates as time goes on, though, as they learn the truth one by one.
- Mako Mermaids: An H₂O Adventure:
- Evie spends the first season as Zac's unwitting muggle girlfriend, unaware of any merfolk activity, but still noticing her boyfriend being secretive about something he's sharing with his best friend and a mysterious new girl. She learns the truth during the second to last episode of the first season, and accidentally becomes a mermaid herself in the first episode of the second.
- Evie's best friend Carly takes over this role in the second season, getting a first row seat to mermaid shenanigans without suspecting anything supernatural... until Evie gets sick, spreads her cold to the other mermaids, and accidentally transforms them in front of Carly.
- Sabrina the Teenage Witch had a few like her boyfriend Harvey and best friends Jenny and Valerie. Harvey eventually becomes more witting after he becomes immune to Sabrina's memory-altering magic.
- In Smallville, all of Clark's friends are initially unaware of his secret. All of them eventually learn it though.
- In What We Do in the Shadows (2019), the vampiric main cast live next door to a human couple called Sean and Charmaine, who are completely unaware of their true nature. The vampires barely even try to hide it, but their neighbours think they're merely a group of slightly quirky foreigners. Despite their general disdain for humans they're oddly fond of Sean (Laszlo in particular considers him his best friend) and they occasionally go along with him in "human" activities (casino trips, deer hunting, watching the Super Bowl) that they wouldn't bother with otherwise.
- In Wizards of Waverly Place, Harper Finkle is unaware that her best friend Alex, along with Alex's brothers Justin and Max, are wizards. Once she finds out midway into Season 2, she inevitably becomes Alex's sidekick in her magical shenanigans.
- Immortal Souls has Friendly Neighborhood Vampire John's Unwitting Muggle Love Interest, Allison. She finds his behavior and physical traits odd sometimes, but mostly worries that he's sick or is having problems rather than thinking anything major is up. Most of the games' plots involve him trying to keep her in the dark about him and the supernatural world even when she's being threatened and/or held hostage by his equally monstrous (but disguised) enemies.
- Trixie and Spud are this to Jake in American Dragon: Jake Long, before they find out early in the first season (after accidentally handing him over to one of his enemies). They become his Secret Keepers and sidekicks from that point, instead.
- Bailey Carter is this to Gretel in Hamster & Gretel, in addition to treating both normal Gretel and superhero Gretel as separate entities, unaware that they are both one and the same.
- In the German show School for Vampires, Sunshine is totally unaware that Oscar is a vampire. She even goes as far as dressing him up as a vampire so he can pretend he is one!