A character spontaneously starts crying, seemingly for no reason. When asked about it, even they don't know why they're doing it. There is inevitably a plot-relevant reason behind this.
Perhaps it's a repressed memory that has just been triggered, or maybe something bad has happened somewhere else and their Spider-Sense is tingling. Whatever the reason, it's usually because their subconscious knows something that the conscious mind doesn't.
Can be Truth in Television. The subconscious can react to things the conscious mind doesn't fully register; for instance, smelling the not-quite-identifiable traces of a perfume worn by a beloved late grandmother. Crying is also a common reaction to being overwhelmed by emotion; such emotional turmoil can be both physically and emotionally painful, and difficult for the conscious mind to completely sort out, leading to things like Cry Laughing and Berserker Tears as one slowly figures out everything one is actually feeling.
- This happens in the end of Kannazuki no Miko; then Himeko, after her love Chikane is erased from existence, (including from Himeko's memory) looks at pictures that used to be of her and Chikane, but now are only of her because of the erase, she starts to cry and she does not know why.
- In Scrapped Princess, Pacifica starts crying when her accidental protector and surrogate big brother Fulle is killed elsewhere, even though, due to a case of Laser-Guided Amnesia, she doesn't have any memories of him anymore.
- In the Karin manga (not the anime), Karin's vampire family removes all knowledge of them from her mind, so she can live happily without their burdens on her shoulders. When Kenta (who knows about the memory adjustment) asks about her family, Karin starts crying, but she doesn't know why. Cue Kenta's marriage proposal to Karin.
- Rei does this on two occasions in Episode 23 of Neon Genesis Evangelion.
- The first is after her conversation with the sixteenth Angel after it forces her to feel sadness. It's not that she doesn't know what sadness is, just that she's actually feeling physical manifestations of emotion.
- The second is after she tries to destroy Gendo's glasses, having lost her memories of her time as Rei II. She feels sadness, but she doesn't know why.
- In the movie of Howl's Moving Castle, this is implied to be the reason Sophie cries as she escapes from Howl's childhood.
Sophie: I'm sorry, Heen. I know I need to keep running. I just can't seem to stop crying, that's all.
- In Mobile Suit Gundam Wing, when Trowa is pretending to be an OZ soldier, he is ordered to shoot down the (unpiloted) Deathscythe Gundam as a test. He does so without hesitation, but is surprised to see his tears floating in the cockpit afterward.
(paraphrased)"Tears...? Are these my tears, really...?!"
- In the 2001 version of Cyborg 009 Joe/009 befriends a little girl named Alice, who can travel through time. She fufills a promise she made to him in the past by allowing him to travel to the past to meet his mother. (And might be said mother or not, but it's not clear.) Joe's tears are initially out of joy. However, his memory of the experience is erased. When he comes to he is sitting on a train, confused as to why he is crying.
- Gunslinger Girl. Claes has this reaction to seeing a movie that subconsciously reminds her of her previous handler, Raballo, who has been wiped from her memory by the Agency.
- In Noein, when Fukuro is killed, across town Ai starts crying without knowing why.
- In Claymore, after Miata's surrogate mother Clarice sacrifices herself to save Miata and, with her last strength, manages to erase Miata's memories of their time together, Miata still bursts into tears and cannot understand why she is crying for her mother who was killed by yoma years ago.
- In the episode "Runaway Tachikoma" in Ghost in the Shell: Stand Alone Complex, Motoko dives into an unknown cyberbrain to try and recover the technician who went in before her and hasn't come back. What she finds inside is a movie theater, and all the inhabitants inside it can't stop talking or watching it. The result of a director who's trying to create the perfect form of entertainment that never gets boring no matter how many times you see it. Motoko watches it herself, and is started to find that she is crying. Hardly anything gives her such an emotional response.
- In Tokyo Ghoul :Re, Amnesiac Hero Sasaki begins crying suddenly after tasting the coffee from the titular shop, :Re. He's immediately puzzled, with no idea why something so simple would bring him to tears. It's because the shop is run by the survivors from Anteiku, and he unconsciously recognizes the taste.
- In episode ten of Tokyo Magnitude 8.0 Mirai begins crying when she visits her brothers classroom. She doesn't understand why she is crying at the time. Yuuki had died a day or two earlier but as a coping mechanism her mind blocked it out and she could still see him as if he was alive. The scene is the start of her remembering he has died.
- In One Piece's Thriller Bark arc, Chopper learns that the zombies, rather than people brought back to life, are actually just corpses that have been animated by a Devil Fruit power. He gets especially infuriated when the evil Dr. Hogback treats his zombie maid Cindry like an Extreme Doormat, lamenting Cindry's current state and that a human has more freedom than that. At some level his words strike a chord, causing tears to pour from Cindry's eyes, but, as she says, she doesn't know what's going on. As Robin says afterward, it was probably the only true miracle on Thriller Bark.
- Inside Mari is a manga about a man who bodyswaps with a teenage girl, or at least so it seems. While looking at family photos, Isao discovers a photo that was ripped in half but taped together again. Touching it triggers a memory of Mari on a ferris wheel as a child and ends up making Isao cry. It turns out to be due to memories of Mari's deceased grandmother.
- Your Name shows this happening several times with Taki and Mitsuha, seemingly because their body-swapping is treated as a dream-like state, particularly the fact that the memories of the swaps fade over time. Notably, Taki starts crying while getting ready for his date with Miki (which Mitsuha set up while she was in his body), and Mitsuha does the same when she realizes they're probably out on their date already; this is the first indication that the two of them have started falling in love with each other. The most poignant instance of this comes right at the end of the movie, when the two finally meet face-to-face several years later, even after completely forgetting each other.
- In Danganronpa 3: Side Despair Izuru Kamakura does this after Chiaki dies in front of him. The tears show that at least some small part of Hajimes' personality survived the transformation into Izuru, as while Izuru had no real attachment to Chiaki, Hajime had a significant crush on her.
- DEVILMAN crybaby has Ryo Asuka suddenly shedding tears over Akira's death — which he was responsible for, mind you — and all the while he's questioning what exactly he's feeling that it's even making him cry.
- Justice League of America: After their attempt to conquer Earth fails when they are found vulnerable to fire, fifty White Martians face the Martian Manhunter. At the end, the narrator tell us of a man that, every morning just after awakening, feels like he had once incredible power that is forever lost. This feeling of loss and frustration is shared by fifty other humans scattered around the planet, and is so big, he wants to cry. But he doesn't, because he is an adult and has no time for such nonsense. So he smiles, goes out and begins his working day as a fireman.
- Avengers: Endgame: Many characters, large and small, break down crying at seemingly random points in the film. No one ever comments on it; the clear implication is that after half the universe dying, everyone is so depressed that no one finds anything odd about people crying for no obvious reason.
- In Star Trek: Generations, Data cries when he finds his beloved cat Spot unharmed in the wreck of the Enterprise D. Not understanding why he is crying in spite of this event making him happy, Data assumes that his emotion chip must be malfunctioning. Deanna tell him that it's working just fine.
- In Soldier, when Todd gets cast out by the junkyard community. As he cries, he wipes and looks at his tear and his reaction to it seems surprised.
- A Song of Ice and Fire. Sansa Stark has this reaction to King Joffrey's death, even though he'd executed her father, had her beaten regularly by his bodyguards, and held her hostage under constant threat of rape or execution. The most likely explanation is a sudden release of stress given that she's had to hide her true feelings for the past two years under a mask of courtesy.
- After the defeat of Shere Khan, Mowgli from The Jungle Book is amazed to see tears falling down his face. Bagheera assures him that this is normal and let him let the tears fall.
- In Those That Wake, this happens due to memory loss. Laura's mom has this happen in the first book, and Laura herself does in the sequel.
- Doctor Who: Amy Pond does this three times.
- The first time, she thinks she's happy, but she's sad because Rory was erased from existence, and Vincent van Gogh can sense it.
- The second time, Rory thinks she's sad, but she's happy because she's found Rory, even though she still can't remember him.
- The last time, she's at her wedding, so naturally Rory thinks she's happy, but she's said because she got River Song's TARDIS-themed diary and it reminds her of the Doctor, who got erased from existence, but he gets better because she remembers his stories.
- On Friends, Phoebe goes through rapid mood swings later in her pregnancy. When she goes from hysterically laughing to bawling her eyes out, she just says "I don't know." in response to Rachel and Monica's concern.
- Kamen Rider Build: Sento Kiryu starts crying after tasting the sweet omelette made by Kyoka Katsuragi. She always prepared it that way for her son and just happened to have it at hand to serve to Sento, when he visited. Turns out, he is her son, who had his identity stripped away instead of being flat out murdered as she was led to believe.
- On LOST, Daniel cries while watching a news report about the Oceanic 815 crash. He says he doesn't know why.
- Kingdom Hearts:
- This happens a lot from Chain of Memories onwards, usually a character crying because of something they can't remember or a link to another character. It happens to Sora more often than anyone else.
- After meeting the Twilight Town gang at the start of Kingdom Hearts II, Sora starts crying just before he leaves to meet Yen Sid. The kids were Roxas's friends in the Lotus-Eater Machine he was trapped in before merging with Sora.
- After the Doomed by Canon protagonists of Birth by Sleep have met their fates, the four-year-old Sora starts crying without realizing it, to Riku's confusion.
- Also in Dream Drop Distance, when Sora meets Xion for the first time.
- In Kingdom Hearts III, Axel finds himself crying after Kairi triggers a vague memory of Xion.
- In Fire Emblem: The Blazing Blade, if you fulfill certain requirements you'll get a secret gaiden chapter in Hector's route. After Nergal's defeat, if you unlocked that chapter Nils will start crying for reasons he doesn't know, but the player has figured out: Nergal was his and Ninian's Archnemesis Dad.
- At the end of Lufia II: Rise of the Sinistrals, Tia, who previously had been Unable to Cry due to overly toughening herself since childhood, suddenly finds herself crying uncontrollably without knowing why. It's because her Unrequited Love Interest, Maxim, has just died.
- In Disgaea 3: Absence of Justice, Princess Sapphire established herself as someone who is incapable of crying. When Almaz dies, she doesn't shed a tear, only going on about how sad she is. When Almaz comes back to life, she's overjoyed, then confused at the tears streaming down her face.
- The final ending of NieR has Kaine start crying when she finds the flower given to her by the title character, who just sacrificed his very existence to save her own (meaning she can't remember him).
- During Issue #10 of The Secret World, players find themselves reliving the memories of the last major visitor to the Dream Palace's A/V room, a rather confused young man named John Copley. During his visit, John found himself sitting on the floor, staring at the wallpaper - only to experience a vision of the Dreamers devouring the world; according to his narration, he found himself crying but not fully understanding why. Given the magnitude of what he just witnessed, part of it's down to Broken Tears. Unfortunately, the other half of it's due to Tears of Joy: John has finally found his purpose in serving the Dreamers as a Morninglight cultist.
- Played for Laughs in El Goonish Shive, after Justin encounters a creature seemingly made of fire that doesn't burn. Cut to:
Student: Why are you crying, Dr. Physics Professor?Professor: I... I'm not sure...
- In Welcome To Room 305 after Jung Hyung calls Rose a pervert and says any relationship with her would be impossible to Yoon Sung (Rose was eavesdropping), Rose tells Kyung Ah what happened and says she's glad they learnt about their differences now otherwise they'd fight. She begins to cry and has no idea why.
- Autobiographical example in Hyperbole and a Half with the effects of Allie's antidepressants.
"Why are you crying?""I don't know. It's just something that's happening."
- This is the premise behind the Somewhere An X Is Crying trope names.
- The Daffy Duck cartoon Ain't That Ducky has Daffy and a hunter (a caricature and voice of actor Victor Moore) confronting a little yellow duck who does nothing but look into a satchel and cry pathetically. Nobody knows why until the end when Daffy and the hunter get hold of the satchel. A piece of paper that says "The End" is in it.
- Steven Universe: In "Steven's Dream", Steven starts crying heavily in his sleep while having dreams where he's Seeing Through Another's Eyes. What he sees in his dreams doesn't directly explain what's going out, but he follows the clues to find Blue Diamond (who is later shown to have Emotion Bomb powers) mourning on the site of Pink Diamond's death.