Say you have a character that seems to have everything going okay for them, which is then brought to a screeching halt because of this trope where a characters fall from grace is depicted as stemming from them having sexual interaction with another character.
This is sometimes because the character who has sex does it without thinking about whom they are having sex with.note
The one they have sex with could be either: a Forbidden Fruit, someone higher up the social ladder, a Femme Fatale, someone with a lot of power or connections, etc. Of course, sometimes their having a downfall after having sex has less to do with the person and more to do with bad luck.
This compares/contrasts with Death by Sex because a character may either die from the encounter, or go through a Break the Cutie process but not die as a result of their hasty initiating of sex. See also Love Ruins the Realm and Sex Is Evil.
Sometimes Murder the Hypotenuse comes into play here. This can cross over in certain scenarios with Rape Is a Special Kind of Evil. If the character who has the sex is a villain this can be used during a Villainous Breakdown. Considered a Super-Trope to The Schlub Pub Seduction Deduction. Star-Crossed Lovers will sometimes be subject to this trope, because that one moment where they get to share intimacy and feel loved is dashed soon after by unfortunate circumstances and they are ripped away from each other as per the setting, and meet their downfall.
Examples that play with this trope might be where a characters significant other cheats on them with someone else causing that character to snap and fall apart due to that knowledge, leading to their downfall due to Love Hurts. In worst cases, they will actually have the misfortune of witnessing their lover engaged in sex with someone who is not them.
In Music, it's been said the Idol Genre controversy is that Idol Singers should be virgins for their Wota fans' sake, and being caught having sex or a relationship is marked as a "crime" for their fans to the point of being seen as the singer's downfall (like the known case of seiyuu and singer Aya Hirano, for example). This is called Contractual Purity.
- After Guts leaves the Hawks, Griffith, devastated by this, seeks out some sexual solace with Princess Charlotte. And the countdown to The Eclipse and his downfall which encourages him to initiate the sacrifices necessary to gain Godhood, starts the second her father finds out.
- Casca is raped by Femto/Griffith her former beloved commander after having her comrades die in horrific ways. Because of this she retreats into herself and regresses into a insane childlike state, which is a far cry from her mouthy and fiery Action Girl status from before.
- Guts was raped as a kid by a man his adoptive father sold him to for one night. He was also betrayed by Griffith from his raping of Casca and sacrificing him and everyone else right after had gotten his life somewhat in order and became a Official Couple with Casca who became insane from the rape. This all nearly breaks him completely. Its safe to say that if Guts and Casca had not consummated their relationship with sex and tenderness, Griffith would not have gotten so dangerously jealous leading to Guts and Cascas downfall and Griffiths downfall and resurrection as a Godhand.
- Domestic Girlfriend: Natsuo is an Ordinary High-School Student with a heavy crush on his teacher, Hina. After being constantly frustrated by Hina stringing him along, Natsuo eagerly accepts the request by a girl his age to have a one night stand. However, it turns out that the girl is Hina's younger sister Rui...and also, their mother has now become married to Natsuo's father, making them all step-siblings. This alone was enough to make things awkward and create rifts in the family home, but after Hina learns that Natsuo and Rui had sex, she moves into her own apartment where she and Natsuo can finally sleep together. The two even sleep together during a school trip, where they are caught on camera before and after the act—leading to Hina being forced into transferring schools and their parents contemplating divorce for the sake of their family.
- Kaze to Ki no Uta: Gilbert was assaulted from a young age which led to his promiscuity with other men and therefore his downfall due to his immense self hatred and suicidal attempts as a result from the trauma.
- Happens a couple times to many characters in Sakura Gari. Souma was abused sexually for his beauty when young and he is clearly going downhill in the present where he is promiscuous from the rape and has sex with whoever takes his fancy. His lovers tend to meet a bad hand as well. Also, Souma forces Masataka to work off his brother's debt with sex... (but said brother was dead, and Souma hid that from him.) Souma is madly in love with Masataka (but very bad at expressing it), and it all sends both on a downhill spiral, with Masataka just barely managing to scrape by somewhat unscathed. Kastsuragi is a sexual deviant who abuses his wife and is in love with Souma. He rapes him as a child, and Masataka out of jealousy for the love Souma has for Masataka. Karma rears its head when Masataka throws boiling water in his face post rape and Souma finds out what Katsuragi did to Masataka, responding by poisoning him and egging his abused wife on to burn him alive. The once powerful depraved man dies a well deserved humiliating death.
- In Texhnolyze, Ichise gets poked in the eye in the first episode by a women who hired him for sexual services, causing him to defend himself using his fists. Unfortunately for him, that woman belongs to a major criminal organization, which retaliates by cutting off his right arm and his left leg. He later gets some Artificial Limbs but it definitely contributes to his downfall and eventual death.
- Tokyo Ghoul: In the sequel manga Kaneki has sex with Touka and lets down his guard from it, because he finally found happiness and love with someone. Furuta, his enemy, tries to use Mutsuki's murderous jealousy over Kaneki and Touka having consummated their relationship to his advantage, by having him target those Kaneki loves, namely Touka. In essence, Kaneki's feelings and moment of intimacy shared with Touka put her and those connected to him at risk, and given they (especially Touka) are his Living Emotional Crutch this nearly proves to be his undoing. In truth he has a breakdown, transforms into a uncontrollable monster and nearly loses himself to his rage and despair. His intimacy with Touka nearly made him lose but it also helped him get back up again. Luckily, things work out and Touka and Kaneki live happily ever after with child.
- Sin City: In "The Hard Goodbye", big, tough bruiser Marv has sex with a prostitute named Goldie which is his first and only moment of tenderness and happiness with a woman. It turns out, however, that Goldie was hoping that sharing a bed with Marv would protect her from the people out to kill her, but it didn't work. Marv, feeling a sense of obligation about avenging the only woman who showed him affection (even if for selfish reasons) leads to him declaring war on the corrupt Cardinal Roarke and making enemies of the entire Roarke family. Though he does manage to kill the Cardinal, the story ends with him confessing to all the murders committed by Roarke and his goons to save his mother's life and being executed.
- The Ultimates: Tony Stark's downfall begins after he starts a sexual relationship with Natasha Romanova, aka the Black Widow. In the second volume of the series, Natasha is revealed as The Mole and betrays the team, leading to several members being killed or captured (or, in the case of Hawkeye, his family being killed). In the third volume, Tony has developed an even heavier drinking problem, a sex tape featuring himself and Natasha has further disgraced the already-fallen Avengers.
- A Clockwork Orange: Alex's obsession with sex and violence (sometimes both at the same time) and his steadfast pursuit to inflict both gets the law on his tail, and leads to him getting punished by being jailed for two years and then reformed into a more normal person by torture, which makes him feel physically sick whenever he tries to do anything sexual and violent. After becoming more vulnerable he also is targeted by the victims he tormented when he was at his most insane and violent.
- Damage: Jeremy Irons plays an MP who becomes obsessed with his son's girlfriend Juliette Binoche, begins an affair with her, is found out, and loses everything as a result.
- Election (1999) has various examples:
- Mr. Mc Callister's friend Dave has sex with student Tracy Flick. When the affair is discovered, Dave loses his career and marriage and ends up in a dead end retail job.
- Mr. Mc Callister himself has an affair with Dave's ex-wife; when she confesses to Mc Callister's wife, it destroys their marriage (and caps off a day of him being injured, losing his job, and eventually leaving town).
- Subverted with Paul, who has sex with a girl his lesbian sister has a crush on, who eventually cheats on him. He simply moves on with his life, none the worse for wear.
- Downplayed in The Name of the Rose. Adso ends up sleeping with a young peasant girl (who's used to sleeping with monks for food) and rushes to confess to William, who ends up convincing him it's not the end of the world. It doesn't lead to any further trouble for Adso except that he feels even worse about it when the girl is executed by order of the Inquisition.
- In the movie "Ode To Billy Joe," the male lead gets drunk and has sex with someone who turns out to be his boss (who's a man). This leads to him despairing about his sexuality and ultimately his suicide, leaving his boss and girlfriend to pick up the pieces.
- The Rocky Horror Picture Show: Things go downhill for Brad and Janet following the both of them being seduced by Frank, and then Janet's further sex with Rocky. This damages their relationship, causes Frank to go into a jealous rage, and leads to them being "conquered by darkness", according to "Science Fiction / Double Feature"'s Dark Reprise.
- Titanic: Rose and Jack have a thing together and consummate their love in a car in the bottom of the infamous ship. Rose's fiance Cal is very possessive and wanted to share intimacy with her and once he finds out their love for one another he tries to kill Jack twice. Jack ends up dying at the end anyway and Rose has to grow old without him. Meanwhile, Cal succumbs to despair after losing Rose (he thinks she died on the Titanic to boot) and as the years pass its said he lost his money and committed suicide.
- Lovelace's rape of Clarissa in Clarissa counts, as it drives Clarissa to madness, and results in Lovelace's death in a duel.
- The Epic of Gilgamesh: The gods create Enkidu so as to provide Gilgamesh (who is two-thirds divine and one third mortal) with someone who can actually rival him and remove his arrogance. He is first found by a hunter (freeing the wild beasts from the hunter's traps), and on Gilgamesh's advice, the temple prostitute Shamhat is sent to seduce Enkidu. After six days and seven nights of nonstop sex, Enkidu tries to return to the wilderness, but the animals flee him. Unable to return to the wild, Enkidu becomes a civilized man through Shamhat's teachings and eventually Gilgamesh's friend (and dying of illness, prompting Gilgamesh to try and fail to bring him back).
- Played with in You, in a couple of ways:
- Joe thinks he and Beck are happy together, and the only thing that curtails this is learning that Beck has been cheating on him with Dr Nicky.
- Joe's total horniness for Beck will often get in the way of his judgement, to the point where he kills almost anyone who has meaningful sex with Beck.
- In Buffy the Vampire Slayer, in the Surprise/ Innocence two-parter, Buffy and Angel having sex is what gives Angel a "moment of perfect happiness". This causes him to lose his soul, turning into psychopathic mass-murderer Angelus and the Big Bad for the rest of Season 2.
- There is a lot of examples from Game of Thrones:
- Before the beginning of the series, Prince Rhaegar Targaryen abducted Lyanna Stark, even though Lyanna was betrothed to (and loved by) Robert Baratheon. This act led to Robert's Rebellion, where Robert usurped the Iron Throne and killed all of the Targaryens save two. Actually three, since it's later revealed that Rhaegar and Lyanna were actually in love and she begged her brother Ned to protect her newborn son from Robert by changing his identity.
- One of the major rifts between King Robert Baratheon and his wife Cersei Lannister was the fact that Robert openly whored around and fathered bastard children with as many women as he was able. This led to several other examples:
- Cersei openly slept with her brother Jaime and bore three children from him while pretending they were Robert's. After this is found out, it leads to a bloody civil war that encompasses most of the series.
- Cersei also slept with her cousin Lancel Lannister and seduced him into helping assassinate Robert. This not only leads to the aforementioned Civil War, but allows a religious fanatic group called the Faith Militant to publicly shame Cersei herself, as well as forcefully recruit Lancel.
- Margaery Tyrell is a beautiful and charismatic woman who desires to be queen. After marrying Renly Baratheon and later Joffrey Baratheon, both men are assassinated not long after. She then quickly marries Tommen Baratheon, who is much more Weak-Willed than her previous husbands and uses sex to bend him to her will. This leads to a feud between Margaery and Cersei which finally ends when Cersei blows up the Great Sept with Margaery and many others inside (including Lancel Lannister). Tommen then kills himself right after, leaving Cersei childless.
- Stannis Baratheon converts to the religion of the God of Light while being seduced by a Red Priestess named Melisandre, who promises to "bear him a son". Melisandre instead gives birth to a creature called a Shadow which bears Stannis's face and murders Stannis's brother Renly (who is a rival for the Iron Throne). Further listening to Melisandre leads to Stannis burning his own daughter at the stake, fighting several lost battles, and the Shadow incident comes back to bite him when Renly's knight Brianne finds him and beheads him for the murder.
- What finally makes Tyrion Lannister snap and kill his father is finding his former lover, Shae, in Tywin's bed shortly after Tywin sentenced Tyrion to death for a crime he didn't commit. Tyrion then murders both and sinks into despair.
- Danaerys also has several examples:
- The Dothraki tend to Rape, Pillage, and Burn settlements for wealth and power, and this leads to them gangraping one shaman woman whom Danaerys takes pity on and tries to save. When Danaerys's husband Drogo is later fatally injured, Danaerys begs the shamaness to save him—instead, she not only condemns Drogo to to live braindead but also destroys Danaerys's unborn child and makes her unable to have any further children.
- Danaerys later falls in love with Jon Snow, who turns out be the child of Lyanna and Rhaegar—and therefore her nephew. This obviously leads to a rift in their relationship as well as another question of who is fit for the throne. The loss of Jon's love, as well as several other traumatic incidents, leads to Danaerys snapping during the final battle at King's Landing and massacring the entire town, then giving a grand speech with plans to do the same throughout the rest of the world. Still in love with Jon, Danaerys tries to convince him to rule at her side, but Jon instead stabs her through the heart and murders her.
- Kaamelott: Despite receiving plenty of warnings both mundane and supernatural not to sleep with Mevanwi, Arthur ends up doing so and the kingdom very quickly falls into ruin, not least because Mevanwi turns out to be an evil bitch unwilling to give up her new position or work with the Round Table to lead the country.
- Supernatural: Ruby kisses Sam when he is at his lowest and most vulnerable point in the wake of Dean's death, to prove to him that he still has her, at least. He tries to put some distance between them and rebukes her, but she keeps pushing it until he gives in, kisses her back (rather desperately), and has violent, desperate, hair-pulling sex with her. Rather than this showing two people coming together for comfort, it just goes to show how Sam has hit rock-bottom after Dean died. Sera Gamble even compared it to self-mutilating and calling it getting dressed for the prom.
- Veronica Mars: in a very delayed example, the Big Bad of Season 2, Cassidy Casablancas, might've escaped detection for other crimes, including the bus crash, if he hadn't raped Veronica years before.
- In King Arthur, the events leading up to Camelot's fall began with Lancelot having an affair with Arthur's wife, Guinevere. When the adultery was discovered, Guinevere was set to be executed, prompting Lancelot to interrupt the execution and slaughter Gawain's brothers in a mad rage. This spurs Gawain to declare war on Lancelot against the wishes of his king, leaving the kingdom to Mordred, who proceeds to rebel against Arthur.
- King David's greatest mistake started with this. He saw a woman named Bathsheba bathing when he was looking out on his city one night, they slept together, and he had her husband killed to hide the fact that it got her pregnant in the Trope Namer for the Uriah Gambit. A number of family problems would ensue after this, culminating in his son Absalom's rebellion and Adonijah attempting to proclaim himself king close to David's death.
- Samson had a lust problem, and the Philistines he tormented used this against him by bribing a prostitute named Delilah to try to learn his secret. He eventually caves, and is captured and humiliated as a result.
- In Ruy Blas by Victor Hugo, the action starts when Don Salluste is kicked of his political positions and exiled from the court due to seducing and fathering a child with one of the Queen's ladies-in-waiting (he himself calls himself an idiot over it). This leads him to concoct a plan wherein his lackey Ruy Blas poses as a nobleman, seduces the queen, and then is found out, humiliating the queen if not seeing her banished. Unfortunately, Ruy Blas is in love with the queen, and uses his position to actually do good (not to mention having no intention of sleeping with her).
- Hamilton: Alexander Hamilton's fall from grace is catalyzed by his brief affair with Maria Reynolds. Maria's husband James blackmails him with the information, leading Hamilton to shell out money to keep it hush-hush. When Hamilton is suspected of shady financial dealings, he publishes his account of the affair himself, leading to a drop in public opinion from which his reputation never recovers.
- Played with in Measure for Measure. Angelo's downfall appears to be sex (and he is definitely not happy about eventually having sex in a Bed Trick with Mariana), but it's arguable that his unhealthy attitude to sex is actually responsible.
- A Streetcar Named Desire: Blanche sees herself as a southern belle with fading beauty and flirts with and teases Stanley, Mitch, and the delivery boy because she is so desperate to be seen as attractive to the opposite sex, (something she never felt because her husband, Allan, was homosexual). And when Mitch expresses genuine interest in Blanche, he seems to be receptive to her attempts. Once Stanley digs up Blanches past lies and trysts and reveals them to Mitch, however, this is the beginning of her downfall, and results in Blanches inevitable disillusionment that she has still failed to find a man who truly respects her. Stanley, with his animalistic brutality is fully exemplified as he carries her to the bed. Though Williams does not explicitly describe the graphic rape, we can infer its occurrence. We have seen Stanleys propensity for violence throughout the entire play, and his desire to exert total control over others is hardly surprising. The rape is the culmination of Blanches failed attempt to redefine herself in New Orleans, and is the physical corruption component of the tragic characters (Blanche) downfall.
- In Bojack Horseman Mr Peanutbutter puts his relationship with Pickles in danger by sleeping with Diane, twice. Similarly, while he didn't end up going through with it, one of Bojack's biggest regrets is almost sleeping with Charlotte's 17 year old daughter Penny.