Apparently, mysterious phenomena come in groups of seven.
Why? Well, that's a mystery. There's probably six more.
An urban legend especially common in a Japanese school setting, these tend to be awkwardly brought up during summer episodes, where mysterious legends are attributed to a not-particularly-old place. Nearly always end up being complete horsehockey, except for perhaps the last one. Common themes include voices in an empty room, faces in a wall, staircases with more steps going up than coming down, and other variously spooky and paranormal things.
Note that this is not the same as there being seven Objects of Power, or other Numerological Motifs associated with the number seven - it's specifically the Japanese cultural phenomenon of places with seven unrelated but strange and mysterious things that happen in an otherwise normal place.
A common punchline is for the seventh mystery to be that there are only six mysteries.
- Ikki's school in Air Gear has seven mysteries, most of which are explained by the presence of a secret room Kogarasumaru eventually uses as their home base.
- In Attack on Titan: Junior High, the "Seven Mysteries of Titan Junior High". Armin apparently is knowledgeable about them. As it turns out, they are a prank created by the Survey Club's members to make the test of courage more fun, but the seventh mystery appears to be true, since the ghost girl mentioned by Erwin is actually Frieda Reiss, implied to be a senior before she becomes a ghost.
- A series of omakes in the Bleach anime had Ichigo investigating seven unexplained phenomena in Karakura Town, which invariably turned out to be his friends dicking around. He stops investigating after the sixth, having caught on; good thing, too, because the seventh mystery turned out to be Kon harassing women while in Ichigo's body. Kon wisely decides to keep that a secret.
- Comes up between story arcs in Blue Exorcist. The mysteries range from strange noises coming from one specific toilet stall to a house that never seems to get closer as you walk toward it. In a subversion, all seven of them turn out to actually have supernatural origins, no matter how mundane they sound.
- Call of the Night has Yamori and his friends sneak into their school at night to have fun while verifying the seven mysteries. There's two snags, however: first, there are actually nine mysteries, one of which involves a statue that their school doesn't even have; and second, the ninth mystery is about a teacher that went missing ten years ago, who apparently can be found in one of the classrooms at night. Said teacher turns out to be a vampire who hasn't eaten in ten years and who loses control and attacks them after being found.
- Shows up during in The Devil is a Part-Timer! as the characters are trying to find a way to get more magic. It turns out there's only six mysteries, since finding the seventh (allegedly) triggers a call on your cellphone which will cause you to disappear. Naturally, the heroes immediately ask:
- 1. How does anyone know what happens if you disappear as soon as you find out?
- 2. Why would a decades-old legend involve modern cell phones?
- Dirty Pair Flash manages to set up a High School AU situation in its second season as an excuse for this plot. It turned out to be a "Shaggy Dog" Story and a "Scooby-Doo" Hoax as the school was part of a planetwide amusement park and the "ghosts" were All Part of the Show.
- In The Doraemons Special, Nobita and Matadora uses the seven mysteries to scare off two robbers from the school at night with the help of their gadgets.
- A major plot point Dusk Maiden of Amnesia. The Paranormal Club believes that finding all seven mysteries will help them discover the secrets behind Yuuko's murder. Much of the plot involves distinguishing between rumors or ghost stories and true mysteries.
- The third episode of Fairy Musketeers revolves around the seven mysteries. They all turn out to be caused by the heroine, Akazukin.
- In GeGeGe no Kitarō's sixth iteration, Neko-Musume explains to Mana that schools are often places where Yokai haunt and that each school has their own Seven Mysteries, which Mana lists down: the art room design statue that cries blood, the laughing anatomical model, the running statue of Kinjirō Ninomiya, the Jinmenken that lives in the connecting corridor, the portrait of Beethoven that comes out and plays the piano, Hanako-san of the third floor's girl's bathroom and Yōsuke-kun of the second floor's boy's bathroom. Later after Yōsuke-kun was defeated by Neko-Musume for kidnapping the other five and stalking Hanako-san, Nurikabe became one of Mana's school's mysteries, due to his infatuation.
- The first episode of Haunted Junction had the Power Trio searching not just for the Seven Spots, but for the seven ghosts associated to them. Hilarity Ensues.
- JoJo's Bizarre Adventure:
- Diamond is Unbreakable: The town of Morioh develops its own wonders that soon become landmarks, such as Angelo's Rock which becomes local spot for couples, and a cliff that holds a bouncy rock at the bottom.
- Stone Ocean: Played for Laughs with the Seven Mysteries of Green Dolphin Prison. They don't relate to any of the prison's actual mysteries, they're just a tongue-in-cheek way the inmates can complain about the workings of the prison. One of these mysteries is how, even though there should be a meal for every inmate, there'll be none left for anyone who arrives last; immediately afterwards, it's demonstrated this is because some inmates will take more than one meal. Because this part is set in Florida, the Seven Mysteries are localized in English as the Seven Wonders.
- JoJolion: Like in Part 4, Morioh has a few wonders that's become common knowledge among the residents. The Shakedown Road that teleports passerby to another location, and The Milagro Man, where someone picking up a certain dollar bill causes an endless Plague of Good Fortune until they end up getting killed by the money.
- The light novel Spin-Off of Kaguya-sama: Love Is War deals with the seven mysteries of Shuchi'in Academy, with the seventh being that anyone who finds the other six will fall to their death. Due to a string of coincidences, Ishigami ends up encountering all six of the non-fatal ones. The final chapter of the book also revealed that all of them (including the death) have a mundane origin from an event 40 years prior.
- In the Toei Animation version of Kanon, after discovering Mai fighting demons at the school, Yuuichi asks Kaori if she's heard of a girl that appears at night. Kaori thinks he's talking about the obligatory "cute girl ghost" of the seven mysteries. However, every single one is completely bogus, including the ghost; Mai's supernatural connections have a very different origin.
- The school in Kekkaishi has 77 Mysteries. The increase is due to the school sitting on the manga's resident Applied Phlebotinum.
- The Kindaichi Case Files story "Smoke and Mirrors" has "The Seven Mysteries of Fudo High." They all turn out to be rumors started to cover up dead bodies hidden in an old building that used to be a lab for a crooked pharmaceutics company. Not to mention there were originally six mysteries.
- Came up in Mahoromatic, with the added twist there actually was a ghost in a classroom (and the swimming pool). The students in question even dismiss the other mysteries as "coming with every school", and concentrate on the two ghost stories.
- One episode of Maria†Holic focuses on the seven mysteries of Ame no Kisaki Girls' School, a high percentage of them involving blood. To the surprise of no one, Kanako is directly responsible for all of them due to her fantasies. Kanako's homeroom teacher later tells her that the seven mysteries applying to the whole school change every year, but seven other mysteries about Kanako's dorm manager have never changed; they range from the genuinely mysterious ("what the hell is her real age?") to mundane Fridge Logic ("why are Virtual Boys not banned along with the other electronics?"). If anyone happens to learn all seven mysteries, the dorm manager will do...well, something, anyway.
- In My Hero Academia, before inheriting One for All, Midoriya mentions that All Might's Quirk is one of the seven great mysteries of the world. What the other six are is yet unknown.
- Mai's arrival at Fuuka Gakuen in My-HiME quickly becomes one of that school's seven mysteries.
- In My Monster Secret, the Seven Mysteries are specifically named, but the protagonists quickly realize that they're the Mysteries; the "Afterschool Vampire" is the series' female lead Youko Shiragami, the "Dwarf of the Hallway" is Class Representative Nagisa Aizawa (a doll-sized alien who pilots a Mobile-Suit Human), etc. However, eventually they realize that these legends have been around for years and thus must refer to the past generation — for example, the "Afterschool Vampire" isn't Youko but rather her father Genjirou.
- My Next Life as a Villainess: All Routes Lead to Doom!: the Portal Book found in the school library is stated to be one of the school's seven mysteries.
- In Mythical Detective Loki Ragnarok, the girl sidekick takes Loki to her school to show him their seven mysteries. As usual, only the last one lacks a mundane explation.
- Nana Fushigi Gakuen actually used this as the title (literally, "Seven Mysteries High School") and featured a pair of ghostbusting schoolgirls. The staircase that has more steps going down than up was the Book Ends for the series.
- Appeared in the later seasons of Ranma ˝, revolving around a "lost school store" and its aged keeper, "the Secret Don of Furinkan High" whose stories of the school's past tied into the Warring States era, WWII, the Mongol Empire, and the Napoleonic Wars (and were, of course, pure fabrication). A later episode introduced an actual ghost girl to haunt the place.
- One chapter of A Room For Two has the main characters investigate the "seven mysteries" of their boarding house, and finding out the truth behind each one.
- One episode of the Sgt. Frog anime has Keroro setting up shop in an abandoned school, planning on staging a few ghost sightings and turning it into a tourist trap to help fund the invasion. He tests out his scheme on Fuyuki and Momoka, who happen to be in the same building on a ghost-hunting expedition, by throwing a set of seven (actually five) "school haunting" cliches at them.
- Student Council's Discretion: The students confuse this with a scary story tournament, so the school ends up with dozens of mysteries, all horrifying. Minatsu undoes it all by adding the legend of the girl who goes around destroying all the ghosts. But Ken's story is the scariest:
Ken: Once upon a time there was a little maid called Kurimu who served her master with all her heart and all her body and all her soul. The end.
- Toilet-Bound Hanako-kun has this trope in spades, with the seven mysteries of the school being like a league of supernaturals that try to keep a balance within the grounds, including helping humans who may be harmed by other supernaturals. Hanako himself is the 7th Mystery and happens to be the leader of the group, though he easily admits that there may be a traitor within the group.
- The Unforgiving Flowers Blossom in the Dead of Night, where the school it takes place in has seven mysteries in the form of horror stories that take the form of Youkai. Each Youkai hunt for human souls while following the rules of their mysteries. Unlike the mention above where there is usually six mysteries with the seventh mystery being "why is there seven", Higanbana somewhat inverts it by having the precedence for an Eighth Mystery in it's first story in the form of one of the protagonists, Marie.
- In Urusei Yatsura, the teacher Onsen-Mark tries to do the traditional midsummer spook-the-youngsters-with-scary-stories routine and mentions the Seven Mysteries of Tomobiki High. Unfortunately, due to the weirdness magnets in the class (Moroboshi and Co.), most of these were already the subject of various previous chapters, and the class was bored.
- One of The Seven Mysteries is the main cause of plot in Uta∽Kata. The rest don't show up.
- Yuuna and the Haunted Hot Springs: Some chapters explore the Yukemuri High School's seven mysteries. Due to the kind of series it is, they all involve something perverted like a staircase that makes others see a girl's panties, a book that turns your clothes into a micro bikini, and a camera that lets you see other people naked.
- The Realm of Spirits in Blank Dream is themed around this. In order to reach your destination, you have to track down and experience six of the seven mysteries; the place where the mirror is locked away is considered to be the seventh.
- In BlazBlue: Continuum Shift, Carl's Gag Reel has him recall the time he, Noel, Tsubaki and Makoto (who he was at the academy with) had him go through one of these because he was feeling homesick.
- A mission late in Crisis Core: Final Fantasy VII has Zack seeking out the seven wonders of Nibelheim, all of which have mundane explanations, and gets him a reward for figuring out.
- In Da Capo II, these mysteries are the basis for a Test of Courage.
- Subverted in Fantasy Life. The seventh mystery of Castele is that Castele has only six mysteries.
- These are mentioned in the "Table For Six" event in Granblue Fantasy. The mysteries involve the strangeness of the main crew, or called as The Grancypher's Seven Mysteries. One of them is what species Vyrn is and why there seems to be four Lamrettas (which is just her talking to herself while drunk). There's also the question of the vast number of characters who were high-ranking officers/knights in other islands and/or those who had been of royalty or noble blood in general.
- The plot of the first Hatoful Boyfriend Drama CD is about Ryouta and Sakuya investigating the seven mysteries of St PigeoNation's.
- Kingdom Hearts:
- In Kingdom Hearts II, part of the extended prologue in Twilight Town features Roxas and his friends investigating "Seven Wonders" that appear to have mundane explanations, while the true explanations are quite extraordinary, the blanket explanation being that they're either glitches in the simulation or Nobodies screwing around with things on purpose... Well, except for the staircase with a different number of steps depending on whether you count them while descending or ascending them. Rai's an idiot and bad at math.
- The Seven Wonders are also in the real Twilight Town in Kingdom Hearts: 358/2 Days, and inspecting Pence's notes reveals that they're all the same as the simulated Twilight Town's with similar mundane explanations, with the exception of an "Eighth Wonder," which turns out to be an invisible Heartless.
- Unsurprisingly, Kotodama: The 7 Mysteries of Fujisawa is Exactly What It Says on the Tin and involves seven mysteries as part of its plot.
- In Little Witch Academia: Chamber of Time, there are also 7 mysteries for Akko and her friend to explore. At least here, Luna Nova is a millenia-old school of magic, making the idea have a bit more merit. In spite of the supernatural school, six of them end up having fairly mundane explanations. the 7th is the actual villain of the game.
- Thors, the military Academy of Adventure featured in The Legend of Heroes: Trails of Cold Steel, has a set of seven mysteries that your main character, Rean Schwarzer, can investigate in an optional quest. All of them turn out to be mundanities: a supposed graveyard that was really just a bad test paper a student buried "six feet under," a "haunted piano" that was really just being tuned, a supposed poltergeist that was just the result of frustrated cooks, etc. The twist is that there is apparently an entirely different second set of seven mysteries also taking place at the Academy that is only briefly alluded to. When Rean asks why she doesn't count the definitely mysterious Old Schoolhouse as one of the seven mysteries, Beryl, head of the Occult Research Society club, implies that of course it's included... in the real seven mysteries of Thors... In Cold Steel II, when the Reverie Corridor appears in the Old Schoolhouse, she tells Rean that he's fortunate to be one of the lucky few that gets to see the truth behind the 'eighth' of the academy's seven mysteries.
- The third Mega Man Star Force game has "The Seven Wonders of Echo Ridge," despite there being only six, as mentioned by an NPC very late in the game, after no doubt having driven batty many players who thought to look for them all out of curiosity.
- Morenatsu has Kounosuke invite Torahiko, Shun, and Hiroyuki into a Test of Courage to find the seven mysteries from their old school.
- The whole plot of Mysterious Forum and Seven Rumors is centered around the titular seven rumors posted on a mysterious forum.
- In Paper Mario: The Thousand-Year Door, the Glitz Pit has its Seven Wonders that one of the NPCs tell you. It turns out that they are all true, and you must investigate them to advance the plot. Of course, in typical Mario fashion, these Seven Wonders have some humorous explanations and aren't all that mysterious given what Mario has seen in the past.
- PARANORMASIGHT: The Seven Mysteries of Honjo centers around a series of mysteries that are linked to a ritual known as the Rite of Resurrection. There are actually nine mysteries instead of seven, and it's eventually revealed that each mystery is actually connected to each other through the actions of an evil onmyoji.
- One of the sidequests in Pokémon Ultra Sun and Moon is searching around a school for seven mysteries given to you by a schoolgirl. After finding the first six, the girl confessed that there’s no seventh mystery, but thanks you for taking your time to help out since these mysteries were scaring her classmates. The girl is later gone. A faculty member reveals that she was actually the seventh mystery herself, being a ghost.
- Ruphand: An Apothecary's Adventure: Arkenvali Academy has a student at its front that references this trope:
Student: Have you ever heard of the seven mysteries of Arkenvali Academy? Of course you haven't! This is a magic school! We don't limit ourselves to just seven lousy mysteries. I think we've got like seventy, at least.
- There's an RPG Maker game called Seven Mysteries, though strangely it's only this trope for the first four chapters. The remaining three deal with the hero of chapter four trying to get to the bottom of everything. As it turns out, a psychotic student had killed seven classmates over a two-week period, framing his last victim, a shy transfer student, for his crimes. The girl's angry ghost was haunting the school, tormenting people who wandered in at night with horrific hallucinations. The headmaster knew about the haunting, but to avoid shutting the school down he conspired with the murderer to kill off the victims/witnesses and stockpile the bodies in a hidden room.
- Apparently, the Seven Mysteries of North High are the subject for Suzumiya Haruhi no Chokuretsu, a game released for the DS in Japan.
- Tales of Rebirth features the "Seven Great Illusions", phenomena which the adventurer Franz is seeking. Three of them are sought during the main story, althoigh the "Garden of Illusion" is quite different from the one found during the story.
- In Touhou Shinpiroku ~ Urban Legend in Limbo and Touhou Hyouibana ~ Antinomy of Common Flowers, Marisa's urban-legend-derived Occult Power comes from this urban legend, including conjuring the incredibly common "walking/running statue" mystery and, for her Last Word, making use of Hanako-san. (A toilet ghost urban legend that sometimes appears as part of the Seven Mysteries rather than a standalone legend)
- Twilight Syndrome has these in the aptly-named "Hinashiro High School's Seven Mysteries" chapter which involves investigating six of them, since the fourth one was a rumor that two of the male teachers were in a secret relationship. Pretty much all of them turn out to be mundane, such as a statue bust rumoured to cry tears of blood because of a human skull embedded in it was actually a novelty money box, ghosts talking in the library at first appears to be two male teachers in a secret relationship, but they're actually holding a mahjong party with the other teachers after hours, with the prior conversation actually being them being afraid they'll get caught holding these parties. Eventually, the main trio get pissed and are about to head home, only to investigate the remaining one about a phantom runner on the track. It's a Living Statue of Ninomiya Sontoku who just sprints away, which the girls are a bit startled by, but ignore it and just go get ramen.
- World's End Club: Yuki considers Kansai's hammerspace baseball bat as one the seven wonders of the world, being curious about how he manages to store it somewhere when he's not using it.
- Yakuza 3 has a chain of substories in which Kiryu investigates the "Seven Mysteries of Ryukyu" that he overhears three schoolgirls discussing. As with most instances of the trope, none of them have supernatural causes, and Kiryu himself ends up contributing to the final legend!
- Yo Kai Watch 1 chapter nine, "The Extreme Dare", involves investigating one of the seven mysteries of the local school.
- hololive ERROR: A magazine describes being trapped in a classroom with floating furniture as one of them, and another one is the story of an art student who bled herself out to use her blood as paint.
- Pokétoon: "I've Become a Gengar" has a band of students investigating their school's Seven Mysteries after dark. Six of them are caused by Ghost-type Pokémon that love playing pranks; the seventh is an unexplained phenomena that traps anyone who's still on school grounds by sunrise.
- Legends about ghosts playing Moonlight Sonata after hours. Sometimes it's played by no one, but often if it's visible the ghost looks like Beethoven.
- There are several common ones revolving around statues coming to life in some fashion.
- Kinjirō Ninomiya, a famous scholar & common subject of statues (especially in front of Japanese schools) is a common one of these. He's often seen running.
- And of course there's the famous Hanako-Chan, the girl ghost who haunts elementary school bathrooms.