A character starts out significant and important on their own, playing a valuable role in the plot. Then they become another character's love interest. Suddenly, the story stops paying them as much attention as before. Narrative-wise, the character is now mainly treated as "X's wife/husband/girlfriend/boyfriend", essentially turning into a supporting character for their partner. Sometimes other characters even stop mentioning the character's previous accomplishments, while their partner's deeds are still remembered and talked about.
For this trope to be in play, the following conditions must apply:
- Only one of the partners is "demoted". If both partners get more-or-less equally Demoted to Extra at roughly the same time, this trope does not apply. E.g., neither Eowyn nor Faramir from The Lord of the Rings fit this trope because both became background characters soon after they fell in love.
- The character played a more important role before becoming a love interest. If the character was already not quite significant before, and simply switched their focus to a new romantic subplot, this trope does not apply. E.g., Nymphadora Tonks and Fleur Delacour from Harry Potter don't fit this trope because they weren't more significant characters before they became love interests to Remus Lupin and Bill Weasley, respectively. Conversely, Jadzia Dax from Star Trek: Deep Space Nine didn't get noticeably less focus or characterization after becoming Worf's fiancee and, later, wife.
A subtrope of Demoted to Extra and Satellite Love Interest. Not to be confused with Promoted to Love Interest, which is about a character who's turned into a Love Interest (but not necessarily a Satellite Love Interest) in an adaptation of the original work. See also Career Versus Man, Family Versus Career, Quitting to Get Married note
Please don't use this trope as an excuse to bash characters whom you dislike for X/Y/Z motives. Becoming a love interest doesn't immediately equal being demoted to SLI, and many accusations fit less in this trope and more in Die for Our Ship.
- Syaoran Li of Cardcaptor Sakura started off as The Rival and for a while had almost equal footing with Sakura, his own supporting cast and many limelight episodes (so much the English dub tried to play him as co lead with Cardcaptors). After Sakura becomes Master of the Cards, the rest of the main arc must be resolved by her with the others providing marginal assistance. As such, most of Syaoran's spotlight at this point consists of one or two short scenes concerning his growing crush on Sakura (he does still get limelight episodes but they revolve entirely around being a love interest).
- Dragon Ball Z: Android 18 was introduced as an independent villain alongside her brother, but then receded into the role of Krillin's wife and more-or-less retired from fighting. She does participate in trying to stop Beerus during Bulma's birthday party, and lampshades the fact that she's still stronger than Krillin when he goes off to face Freeza's army when the villain returns to life but agrees to stay behind to protect their daughter.
- Videl was introduced as a powerful fighter and someone who was suspicious of Gohan and the other Saiyans' unusual power. But once the Buu arc got serious she was sidelined and after marrying Gohan and giving birth to Pan she seems to have retired from fighting.
- Fairy Tail: Juvia Lockser (just like Android 18 of DBZ) was initially introduced as an very powerful antagonistic character to the protagonists, however after meeting Gray, her character begins inexorably to turn exclusively around his after the Fighting Festival Arc.
- Even Levy's character follows the same process, falling in love with Gajeel (someone who at first did not have any qualms to impale her to a tree and to torture her and her friends for an entire night) to the point of making us forget that she had started as a potential best friend of Lucy and one of the cleverest mages of her guild.
- Genshiken: Sasahara's character arc focuses exclusively on his relationship with Oguie after they finally get together. After the series was Un-Canceled as Genshiken Nidaime, Sasahara went from the main character to Demoted to Extra as the focus shifted squarely to Oguie as the new main protagonist. This makes perfect sense, as Sasahara graduates, has little reason to interact with the other characters, and moves Out of Focus, and Oguie takes his place as president of the titular club.
- Katekyō Hitman Reborn!: There are examples of this in both the anime and manga:
- Poison Scorpion Bianchi started off as a pretty capable hitman who could turn everything into poison. But she was also the titular Hitman Tutor's lover, and by the Future Arc she is reduced to an older sister figure for the girls.
- Lal Mirch is probably the most badass character in the series, she has strength, agility, incredible weapons and she even trained one of the Strongest Seven, being chosen for his position initially. And yet everyone just recognized her as one of the Arcobaleno's Love Interests and as one half of the token het couple.
- In the original Mobile Suit Gundam, Mirai Yashima takes on the important role of first mate and helmsman of the White Base, but when she reappears in Mobile Suit Zeta Gundam, we find that she married Mr. Bright and started a family with him. And even though her husband soon becomes one of the key figures of AEUG, she makes very few appearances, instead staying on Earth to take care of her children. That said, most fans remember Mirai more for being able to get a huge spaceship to dodge laser blasts than for starting a family.
- Sailor Moon: Mamoru aka Tuxedo Mask suffers this in the anime, but not in the manga. In the manga Mamoru is one of the most important and developed characters: while somewhat weak on his own, the major villains are usually defeated by combining his powers with Sailor Moon's. His future as King Endymion is also of great importance. By the 4th season he becomes the character with the most focus (after Sailor Moon herself), because of his connection to Pegasus/Helios, and his weak health that fuels that arc's drama. Compared to the manga, the anime starts forcing Mamoru out of the focus after the first season. In the first season he still has an important plot role, due to his forbidden love with Usagi/Princess Serenity. However, in the second season his importance gets considerably downplayed — and by the third season onward he's turned into a mere extra, to the point that when in the fifth season he's Put on a Bus, it really lessened the impact that event had in the manga.
- Sword Art Online plays this trope straight, twice, by reversing the roles of the characters involved:
- In the initial Sword Art Online arc, Asuna is a badass, give-no-fucks Action Girl who carries her weight as one of the most powerful and well-known players in the lead group. When the game is shut down, though, she's one of the players who is "captured" and prevented from logging out. Immediately after this, during the ALFheim Online arc, she is a textbook Girl in the Tower held prisoner by the Big Bad (who plans on marrying her in the real world despite the fact that she's comatose, and sexually harasses and/or assaults her on numerous occasions in the game), giving The Hero Kirito all the motivation he needs to beat the game and rescue her. Finally, in the Gun Gale Online arc, she's... Kirito's girlfriend. She has almost no plot significance whatsoever, and does not appear in GGO's game world; all of her scenes are either milling about in ALO wondering what Kirito is doing, or having conversations with him in the real world.
- In the fourth and final arc of the anime, which returns to ALO, Asuna becomes The Protagonist and is finally relevant again, for the first time since the SAO Incident—only to swap roles with Kirito. In this arc, he's the barely-present love interest who has little relevance to the plot.
- Riku is introduced as Wandering Son as a classmate of Maho that she has a crush on. He has a crush on her little sibling at first but eventually they begin dating. By high school though he's pretty much "Maho's boyfriend" when before he had some chemistry with Nitori at least.
- Attacker You!: Sho Tachiki is introduced as You's potential love interest. Like You, he's also a volleyball player and initially serves as a Big Brother Mentor for her, and also has some Ship Tease with You's Friendly Rival Nami. However after the first few episodes, Sho is very soon Demoted to Extra and very rarely appears in the anime. This is a case where we don't even see a Relationship Upgrade between the partners and the guy is only known as "the heroine's object of affection" who is completely irrelevant to the story. To make things worse, in some foreign adaptations, specifically European, the anime is known with a Name and Name title that makes it look like that You and her "boyfriend" Sho are both equally important protagonists.
- In Runaways, Victor was first introduced as a teenaged boy who was fated to become Gert's mortal nemesis when he grew up. He was shown to be highly intelligent and powerful enough to fight off the rest of the team. After the Runaways managed to change his fate, he ultimately became the love interest to the team leader Nico. Since then, Victor's importance and power diminished considerably: e.g. he got outwitted by Chase, the least intelligent member of the team (who had also temporarily turned against his former teammates.) And then, after Nico dumped him, he spent the rest of the series doing almost nothing except ineffectually pining after her.
- Spider-Man: Marla Madison was a scientist who built a Spider-Slayer for J. Jonah Jameson. He subsequently fell in love with her and they eventually married. Since Dr. Madison stopped building Spider-Slayers, she gradually settled down into the position of Jonah's wife as few writers seemed to be interested in developing her as a character (while JJJ continued being important). As she was Stuffed into the Fridge in a recent story, there is now little chance of that being ever rectified.
- In the Flash Gordon comic strip, Princess Aura began as a fairly important character who drove several plots. After her Betty and Veronica love triangle with Dale over Flash was resolved (in Dale's favor), she was married off to Prince Barin and lost most of her agency and narrative importance, making few new appearances and (from what could be seen of those she did make) becoming a much more domestic and pacific love interest than her previous characterization.
- How to Train Your Dragon:
- Astrid is initially set up as a competitive student who's determined to ace Gobber's training and become a fully fledged viking. Hiccup's aversion to fighting irritates her and his sudden improvement makes her suspect foul play, resulting in her following him into the forest to find out what his secret is. After their first romantic encounter she becomes much more subdued, existing solely to provide Hiccup with support and advice.
- The film's sequel How to Train Your Dragon 2 makes a conscious effort to remedy this, giving Astrid an independent solo role while still maintaining her relationship with Hiccup.
- In The Lion King, Nala plays a significant role in getting Simba to return to Pride Rock and face his past, not to mention being a fierce and determined character in her own right. In the sequel, however, she has a maximum of 20-ish lines, and hardly does anything to contribute to the plot besides fighting in the pride-on-pride battle near the end. What makes it worse is that there were many opportunities and times that she could've said or done something of importance, but she still hardly affected a thing through the whole movie.
- The Little Mermaid II: Return to the Sea demotes Eric to a sounding board for Ariel's worries about their daughter's future. Once Ariel turns back into a mermaid he disappears until the climax - attempting an (unsuccessful) Big Damn Heroes moment.
- Koyuki Ayase from the Confession Executive Committee ~Love Series~ becomes this in the adaptations of "Right Now, I'm in Love." and The Moment You Fall in Love, its animated counterpart. Just before, he played a huge role in "Confession Rehearsal"/I've Always Liked You as the active rival in a Love Triangle, and showed how he came to the decision to pursue Natsuki. Now just contrast that here; he's practically defined by Hina's crush on him, having little else to do in the story than call out to her or say hi while she fruitlessly pursues him, and all the drama stems from her insecurities and Kotarou's feelings for her.
- Star Wars: In The Phantom Menace Amidala is the ruler of Naboo who fights bravely for her people. By Revenge of the Sith she's given up the throne and married Anakin, and while she's still a Senator it's all about Anakin becoming Darth Vader because the scene where she planted the seeds that would later become the Rebel Alliance was left on the cutting room floor for some bizarre reason.
- The Good Prince Antar in Black Trillium is a complex character torn between his loyalty to his royal father and to his country and the realization that his father and king has been corrupted by an Evil Sorcerer and pushes their country into ruin and dishonor. In Julian May's sequel novels, his role mostly boils down to being the King Consort and frequent Distressed Dude to his queenly wife, the ex-princess Anigel.
- Invoked in the Robotech Expanded Universe. Miriya was the greatest Zentraedi female ace, and when she got her High-Heel–Face Turn and married Max Sterling, for the rest of the original series she was his counterpart and got equal screentime with him. Then during the Malcontent Uprisings, the brass made the official decision to turn her into a propaganda piece; "homemaker, mother, former freedom fighter." Miriya abided by it, but still played an important role in the finale (and returned to badass status during the Sentinels series).
- Sherlock Holmes: Mary Morstan, a central character in The Sign of the Four, marries Dr. Watson at the end of the book. After that, she's mentioned by Watson once in a while, typically as "my wife" rather than by name. She eventually dies off-page in the interval between two books. A sample of how she typically appears in later stories:
One night—it was in June, '89—there came a ring to my bell... I sat up in my chair, and my wife laid her needle-work down in her lap and made a little face of disappointment. (From "The Man with the Twisted Lip")
- How I Met Your Mother: In season 7 Barney's character is appropriated as Robin's love interest, and his main significance is to be a source of angst for Robin. This makes the single brief look at his perspective in "Tick, Tick, Tick" all the more heartbreaking, as the audience knows that while Robin is busy going through character development and struggling with her personal conflicts, Barney is miserably and silently Out of Focus, waiting for her to address her relationship with him.
- Perry Mason: Defied. Della Street turned down several proposals of marriage by Perry, because she wanted to be a part of his life and she knew that meant being a part of his work — and she expected that to end after marriage.
- Once Upon a Time:
- Will Scarlet was a main character in Once Upon a Time in Wonderland. When he shows up in season four he's credited as part of the main cast, but is quickly demoted to the love interest of Belle. Sometimes his only appearances are holding her hand in the background, and he only has a quick, blink-and-you'll-miss-it, unspoken cameo in the finale. To make things worse for him, Belle herself has rarely been more than the love interest of Rumpelstiltskin in the series, making Will Scarlet demoted to the satellite love interest of a satellite love interest.
- Robin Hood also gets this treatment big time. In his initial appearance he was a fully independent character, but upon his return (and recasting) he became not a lot more than Regina's true love. This progressively gets worse and worse, until Season Five (ironically the season he got a Promotion to Opening Titles) where he is basically a shadow/occasional Dude in Distress until he is killed off towards the end of the season, probably at the actor's request.
- Hook as well in Season 4. He gets defined almost entirely by his status as Emma's boyfriend, and all his storylines revolve around his relationship with Emma. Season 5, however, reversed this by giving Hook a character arc that, while Emma heavily factored into it, spanned other elements and relationships with other characters as well.
- Inverted with Belle, who began entirely as a love interest for Rumpelstiltskin. When she was made a series regular, she started having more agency in the plots.
- NYPD Blue: Once Andy and Sylvia get married and have a baby, Sylvia is relegated to one scene every few episodes at home with Andy and their son Theo. She decides to quit her job in order to stay at home with their son so Andy gets a second job working airport security, meaning we see her even less. Eventually she goes back to work as an Assistant District Attorney just in time to get killed off.
- The Flash (2014): This happened to Julian Albert after he started dating Caitlin about halfway through the show's third season. As she became Killer Frost, his role was reduced to trying to find her a cure, and acting excessively overprotective of her to the point of risking his own life.
- SaGa Frontier 2: The Knights family gets a bad case of this. Cordelia (assuming she marries Wil Knights) and Diana are both exceptional fighters (in Diana's case, more than exceptional), but once they get pregnant, both retire from the battlefield, settle down and raise their children. Even when Wil Knights returns to the battlefield (with his granddaughter as the party leader!), neither his wife nor Diana are there with him.
- Kairi in Kingdom Hearts had limited screentime, but still managed to have her own personality and character arc concerning her anxiety and fear of change based around her Dark and Troubled Past. In Kingdom Hearts II, almost all her scenes and actions revolve around Sora and her love for him and little else (though to be fair, she does have a few short friendship moments with Riku as well.)
- Jude in Tales of Xillia 2 gets this treatment, with most of his sidequests being focused on his relationship with Mila. Unusually for this trope, this may have been an attempt at an Author's Saving Throw, as Jude and Mila's relationship was considered Strangled by the Red String in the first game due to their interactions not being all that romantic.
- In a few Harvest Moon games such as the original game, Tale of Two Towns, and Grand Bazaar all the love interests have hopes and ambitions of their own...until they marry you. It's especially true of some of the women in Tale of Two Towns. For a female main character, the guys will continue to run their businesses and go travelling after they marry. When a male main character marries, the female love interest will not leave your farmhouse. So, Laney gives up on moving to the city and Georgia stops working at her father's stable.
- Literally any female character in a romantic relationship in Sonichu. Not that any of the characters have particularly deep personalities to begin with, but once a woman gets a boyfriend here, she immediately turns into a submissive, stereotypically feminine Flat Character who does nothing except gush over her boyfriend and fulfill his sexual desires. Probably the most tragic victim is Megagi LaSkunk, who, over the course of three appearances, transforms from an aggressive "butch" archetype into Punchy's personal cheerleader.