Alice loves Bob, and Bob loves Alice. But then, it would be too easy if it was this easy: for some reason, Alice and Bob cannot be left to live happy together. Sometimes, this leads to Love Makes You Crazy, when Bob stops acting rationally to stay with Alice. Sometimes, Bob decides to take care of this annoying guy who claims he wants to just be Alice's friend. Sometimes, Alice decides to torture and murder all of Bob's female friends so he won't be distracted by all these, well... Sometimes, Bob coldly decides to sacrifice his True Companions to save Alice.
This is none of these situations. This is when Alice and Bob stay, most of the time, level headed and genuinely try their best to be together, and notwithstanding their success or failure, the Collateral Damage is at least 147 deaths, the destruction of three cities, and maybe even the End of the World as We Know It. Even if it can involve some irrationality (after all, Love Makes You Crazy or sometimes evil), it's not the characters' flaws, but the circumstances that force the couple to go to extreme length to be together. Or, even worse, they didn't even realize what they were doing, and the couple's stubborn insistence on being together results in an unintended ripple effect of death and destruction. In short, this trope is not about characterization, it is about the effects of a relationship on the story and the setting.
This is a trope about how romance can be really, really destructive. That's just what happens when you place the huge power of love into the hands of someone in love. They become irrational, and mad with power. Expect at least one case of Murder the Hypotenuse, especially if there is a Yandere involved.
- Future Diary: By the end of the series, we learn that Yuno and Yukiteru were once this in another world. When Yuno won the right to succeed Deus Ex Machina in the first world, her first act as the new God was to attempt to resurrect Yukiteru. Needless to say, it did not go well. Everything we know of her in the series is the Yuno who has already long since crossed the Moral Event Horizon by abandoning the first world and creating a second where she could replay her day with Yukiteru. It is heavily implied though that they fit this trope very well in the first world before the events of the series and the original Yukiteru's death.
- In Tsubasa -RESERVoir CHRoNiCLE-, Shaoran causes the time to rewind and a lot of characters suffer because of this, in order to save Sakura.
- Also, in X1999, Kamui's wish to get Fuuma back even if it causes Fuuma and the rest of the world harm. Can also be said for a lot of other characters.
- Umineko: When They Cry: Kinzo and Beatrice (and Beatrice and Battler)
- The second half of Full Metal Panic! has this as a major element when Amalgam starts drastically stepping up their efforts to capture Kaname. Kaname is horrified enough by the collateral damage that she actually surrenders, hoping she can at least stall the plans she's critical for from within. Sousuke, on the other hand, doesn't hesitate to go on the warpath to return his Living Emotional Crutch home; and while Kaname does briefly try to dissuade him and cope without her, she realizes mid-It's Not You, It's My Enemies speech that neither she nor Sousuke can tolerate their separation anymore and that they have no obligation to shoulder the blame for an obscenely powerful terrorist organization that has every reason to just leave her the hell alone. Thus, she commands Sousuke to do whatever he needs to in order to rip Amalgam a new one and get her back home, an order he accepts with a very rare smile.
- In The Sandman, Morpheus and Nada make love once. Her home city is reduced to glass shards. It's suggested that had they remained together, the entire world would have been destroyed.
- Star Wars: A lot of people wouldn't have died if Anakin Skywalker never fell in love with Padme Amidala.
- This is one of the themes of Buffy the Vampire Slayer.
- Romeo and Juliet's romance causes six deaths. 1: Mercutio: Killed defending Romeo. 2: Tybalt: Killed by Romeo. 3 Romeo's mother: Died of sadness because of Romeo's banishment. 4: Paris: Killed by Romeo. 5: Romeo: Killed by Romeo. 6: Juliet: Killed herself because Romeo did.
- Love rarely ends happily in the operas of Richard Wagner. (Of course, what did you expect in an opera -- a happy ending?) It causes Senta to jump off a cliff, Elisabeth and Heinrich apparently just to keel over, Elsa to betray Lohengrin and then to keel over, Siegmund to commit adultery with his own sister and be killed by her husband (she dies in childbirth), Gutrune to drug Siegfried into loving her so that ''his'' wife kills him and then burns herself to death, and Tristan to get fatally wounded while messing around with Isolde, the king's wife, who then herself keels over. Only Walther and Eva seem to end up well.
- Romeo's and Juliet's neighbors got off easy compared to the citizens of Rome and Egypt in Shakespeare's Antony and Cleopatra when their affair starts a war and turns all their people against them.
- In Super Mario Bros. Bowser and Mario both love Princess Peach. Bowser kidnaps PP, and Mario saves her. Between them, they cause the deaths of countless koopas, goombas, and other minions that did nothing wrong.
- Gwendolyn and Oswald of Odin Sphere, which is very, very loosely based on Wagner's Der Ring des Nibelungen. They meet on a battlefield and between the two of them have stormed cities and literally gone to hell and back for each other. Without even knowing how the other feels.