Sheryl: You just realized?
First Girl After All is a narrative technique of concealing a character's first Love Interest for as long as possible until the moment when it's most dramatically shocking to the audience, usually at or near the climax of the plot. This is accomplished either by never making it clear who the First Girl is, or by misleading the audience into believing that another character is the First Girl.
After much of the story, we approach The Reveal, the Final Battle, the Grand Finale, or some other tense moment, and it seems like the "Second Girl" in the Love Triangle (or Last Girl in the Love Dodecahedron) is going to win. But something suddenly "clicks", and the story reveals that they first met when they were children! But wait! This could only have possibly happened BEFORE he met the First Girl. This can only mean that the girl everyone thought was the Second Girl is the First Girl After All.
Most likely a subversion of Last Girl Wins and Double Subversion of First Girl Wins, used to embrace it without giving the romantic resolution away to the audience. In a romance plot, this can be considered a Plot Twist if this happens before a romantic resolution is reached.
The trope can also be used as a Continuity Nod if this is revealed after they get together, such as bumping shoulders in a hallway during a flashback that was on screen for a completely different reason, an encounter which can have the byproduct of being this trope.
Related tropes include Love Triangle, Love Dodecahedron, First Girl Wins, Forgotten Childhood Friend, and Childhood Friend Romance, any of which may be involved, as well as either a Flashback or a Prequel.
As this is generally only revealed toward the very end, the example list is generally filled with spoilers and potentially ending spoilers. Read at your own risk.
- Subverted in Boku wa Tomodachi ga Sukunai. It looked like Yozora Mikazuki was the first girl in Kodaka Hasegawa's life, as she was the "Sora" kid that Kodaka made a promise with years ago. And in fact, Yozora put lots of her romantic hopes on the fact that she was the First Girl in Kodaka's life. Then it turned out that Kodaka actually knew and was Childhood Friends with Sena Kashiwazaki long before Yozora even entered the picture, which made her the First Girl instead. Understandably, poor Yozora doesn't take the discovery well.
- This trope served as The Reveal in Candy Candy: A very young Candy once was comforted during and Heroic B.S.O.D. by an older boy whom she dubbed the "Prince of the Hill", but she never learned his true identity. She believed that her First Love Anthony was him and even asked him about it, but Anthony denied it. She also wondered if her Second Love Terry could have been him, but nothing came out of that "lead". And in the very end of the series, she found out... that her and Terry's Big Brother Mentor, Albert Andree, was the Prince. He also was Anthony's maternal uncle who strongly resembled him, her Mysterious Protector and The Patriarch of the Andree clan (for very complicarted reasons): this meant, Candy's "Prince of the Hill" whom she'd been searching for through all of her life had always been by her side in one way or another.
- Played straight twice in Detective Conan, but also toyed with once and subverted at another time:
- The first couple that fits in here is Detective Shiratori and Kobayashi-sensei: Shiratori had always been in love with a girl he befriended when young, and after thinking for some time that she had grown to become Detective Sato (leading to the Love Triangle with Detective Takagi), it turned out "the girl" was Kobayashi-sensei, who to be fair looks a lot like Satou.
- The second one is Heiji Hattori and Kazuha Touyama, if one considers the Crossroads in the Old Capital movie to be canon. (And it has yet to be contradicted by the manga and the anime proper nevermind the below mentioned subversion). A subplot in it had Heiji looking for the Kyoto girl who was his First Love, and it turns out said girl was a Kazuha who had been momentarily dolled-up by her relatives. Therefore, Heiji didn't recognize her until he heard Kazuha sing a song that the "mystery girl" was singing when Heiji saw her.
- The "playing with" situation happens regarding Shinichi, Ran and Asami Uchida. Asami appears and claims that she is Shinichi's First Love, but it turns out her own love for Shinichi was unrequited. In reality Ran has always been Shinichi's first and probably only love, ever since they were little children (long before Asami entered the picture), and Asami herself knew it since Shinichi pretty much told her when he turned down her Love Confession.
- The subversion takes place in one of the movies, since Heiji's Self-Proclaimed Love Interest Momiji claimed that the two made a Childhood Marriage Promise very early in their lives, throwing a huge wrench in Heiji and Kazuha's budding relationship. It turned out, however, that he promised her something else and she mistakenly believed he had proposed to her. Still, Momiji decides not to give up on her feelings for him despite the huge drawback.
- Flip Flappers is a Yuri version of this. The series makes it clear that Cocona and Yayaka were friends since they were kids due to the organization arranging it. However, the series finale reveals Cocona and Papika met each other in Pure Illusion before that took place. Neither of them remembered it due to Laser-Guided Amnesia.
- Love Hina teases whether or not Naru was the girl Keitaro met and promised to meet again when they both got into Tokyo University, while also suggesting it might have actually been Mutsumi. In the end it turns out it was both — Keitaro met both of them pretty much at the same time, his memory merged them into one person, and he made The Promise with both of them. Naru still ends up with him at the end.
- Macross Frontier pulls this in the movie version. Almost immediately in the first part we find out that Alto and Ranka already know each other and Sheryl was only just arriving on the fleet for the first time. It seemed pretty clear that Ranka was the first girl, but then near the end of the second part Alto has a flashback to his childhood when he was still in Kabuki, when he met and inspired a young and unknown preteen singer named Sheryl Nome, establishing that she was the first girl all along.
- Sheryl implied she knew him in the first movie (she was coy about it in their date: more details were out in the novelization before the second movie was aired where she and Grace discussed they met him long ago in Galaxy), plus Alto fell for Sheryl long before he realized it was that girl who gave him the sky.
- Martian Successor Nadesico has this within series continuity with Inez Fressange, aka cute prologue girl Ai displaced in time by 20 years, give or take a few millennia. However, she's still not the first girl if you count Akito's backstory, and still doesn't win. And the first girl? Yeah, still Yurika.
- Naruto: Sakura Haruno is introduced to readers as a potential Love Interest of the titular character in Chapter 3. The other potential love interest, Hinata Hyuga, wasn't introduced to the series until the manga's second arc. In The Last: Naruto the Movie, Hinata's romance with Naruto is fully explained, and we learn that Hinata met Naruto not too long before they enrolled in the Academy, before he met Sakura, making Hinata both this trope and First Girl Wins. Incidentally, the first version of this scene originally appeared only in the anime adaptation, long before Naruto and Hinata became a couple at the end of the series, and was never hinted at in the manga itself. However, because The Last was the first canon movie of the franchise, their first meeting was officially confirmed as canon, although the movie version of the scene was considerably different from the anime one (specifically, in the change of scenery, season, and dialogue, and the inclusion of a red scarf).
- About a third of the way through Psychic Academy we find out that the girl Ai met on that beach was Mew, not Orina.
- RahXephon is an extremely odd example of this. Haruka was Ayato's first love, before they were separated as Tokyo-Jupiter is formed. When they met again, Haruka was 12 years older but Ayato was still 16 just like the day they were torn apart, so he couldn't recognize her until much, much later.
- According to the Sailor Moon R movie, Promise of the Rose, Usagi and Mamoru count as this in their lives on Earth because Usagi actually met Mamoru when they were both little kids. The day Ikuko gave birth to Usagi's little brother Shingo, a no-older-than-5 Usagi brought red roses as a gift and later snuck around nearby hospital rooms, with one of the roses in her hand. She then entered the one where a no-older-than-ten Mamoru was hospitalized, still grieving over the deaths of his parents and his Trauma-Induced Amnesia, and after a short talk she gave him the rose to make him feel better...
- The series isn't even nearly done, but in the fifth volume of Tsuki Tsuki!, Ouka "Sakura-chan" Minami, Shinobu's classmate who somehow is clingy of him very early on the series, turns out to be his Childhood Friend. Kind of justified for him to forget all about her considering he had a Laser-Guided Amnesia after making a Deal with the Devil to save his little sister from a car crash after being that desperate.
- In The World God Only Knows, when Keima is searching for "goddesses" who remember when he'd seduced them, he finally comes down to two girls. At the worst possible time, he finds out that Chihiro actually isn't possessed by a goddess and doesn't remember her seduction, but rather had fallen in love with him on her own long before the story started, making her not only the first girl but also the only girl to fall in love with him without his efforts.
- This turns out to be the case for Tooya and Aya in Ayashi no Ceres, since Tooya once met a very young Aya several years before the story even started.
- When Mary Jane Watson's origin was finally written in the mid-1980s, it was revealed in Amazing Spider-Man #259 that though they did not meet face to face before their first date in ASM #42, Mary Jane had been aware of Peter for years before, having observed him raking leaves through the window of her aunt's house and even feeling a bit attracted to him while in her early teens. Later the graphic novel Parallel Lives revealed that she even had figured out that he was Spider-Man in the night Uncle Ben was murdered, thus making her a Secret Secret-Keeper for a good part of their relationship until the early-to-mid-80's.
- In Babylon 5, we go the entire series believing Lennier came first in the Sheridan-Delenn-Lennier Love Triangle, as Lennier appeared in the first season, while Sheridan was not introduced until season two. The Prequel movie though has a scene where Sheridan and Delenn actually did meet, very briefly and without introduction (or seeing each other, but they did exchange a few lines), during the Earth-Minbari War, ten years before Delenn met Lennier.
- Cloak & Dagger (2018): Tandy and Tyrone first meet as children, when he saves her life during the storm that killed her family. Ten or so years later, they meet again and hit it off, but don't realize who each other are until their powers react to each other.
Tandy: Wait, you're that kid?
- Coupling sort of has this. The episode "Remember This" shows how Patrick met, and was interested in, his final love interest Sally before he started with Susan. Before this point, it was assumed that Patrick had only been with Susan before breaking up in the first episode and taking an interest in Sally.
- Played with in The King of Queens: a priest that worked at Camp Unity, the summer camp where Carrie and Doug attended as kids recalls seeing the two meeting, which they don't recall. Carrie latches on to the memory, which she interprets as a sign of fate. However, Doug later talks to his mother who reveals that he never attended Camp Unity at all: his parents sent him to "fat camp" claiming it was Camp Unity. The kid Carrie met turns out to be Danny. Doug then agonizes as to whether he should tell Carrie the truth.
- In the original Total Recall (1990), we're first introduced to Melina during an opening dream sequence, but the First Girl seems to be Quaid's wife Lori. Later in the film, we find out that not only is his marriage a part of his Fake Memories, but he knew Melina years before the story proper began. Assuming it wasn't all "just a dream", of course.
- Araxie Haldane in King Kelson's Bride. After events conspire against Kelson's first two attempts at matrimony, he decides to propose to his cousin, and we learn he and his other cousins played with her (and her sister) when they were children. Kelson hadn't seen her since then, and there's no portrait of her among the other portraits collected for his consideration, so he spends a lot of time wondering what she looks like before they meet again.
- This plays a role in Agatha Christie's The Murder on the Links. Jack Renaud was in a relationship with Bella Duveen, but thought that he made a mistake when he meets his sweet neighbour Marthe Daubreauil, and began pursuing romance with her instead. Later, he realises that the one he truly loves is Bella as he was willing to be executed for his father's murder in order to remove suspicion from her.
- Persona 3: The first female characters that The Protagonist meets are Yukari and Mitsuru, party members and potential Love Interests whom the character will see far more often than any other girl in the game. They are later joined by Fuuka, and later yet by Robot Girl Aigis. However, after The Reveal, we learn that Aigis actually "met" the Protagonist 10 years ago, when he was a child. In fact, she is the one responsible for all of the events of the game because of that meeting. Except in the Portable version of the game, she is also the one whom is last seen with the Protagonist.
- This can happen in Inazuma Eleven GO Dark, since Endou's wife in this particular game is his childhood friend Fuyuka (rather than his junior-high sweetheart Natsumi, like in the rest of the Inazuma Eleven media.)
- An episode of The Simpsons reveals that Homer Simpson and Marge Bouvier met as kids (and were even each other's first kiss), but didn't recognize the other one when they met again years later as teens because they each had some other distinctive physical trait at the time: in Homer's case an eyepatch from an accident, in Marge's case brown hair because of a failed attempt to style it that left it burnt.