No Loves Intersect

An aversion of Love Dodecahedron (and other polygons). No competition, no rivalries--Cleaning Up Romantic Loose Ends was in play from the very beginning, and everyone falls in line with their destined other in a stable relationship.

It's admirable of the creator to wish that everybody gets their happy ending, but lands the story far on the idealistic side of the Sliding Scale of Idealism Versus Cynicism.

Often, if a character is left out of a relationship in stories that do this, it's heavily implied that the character is gay or lesbian.

Compare with Pair the Spares (the Love Dodecahedron version) and No Going Steady, which breaks up Love Dodecahedrons in a more chaotic fashion...

Anime and Manga

 * Except for Ling's short-lived, played-for-laughs flirting with Winry and some references to early rivalry between Ed and Al over her, the Fullmetal Alchemist manga and second anime adaption are like this. This lack of love triangles may account for why many fans of the series declare their favorite couple to be completely canon, despite the fact that no popular couple entered a real relationship during the bulk of the series,.
 * As opposed to the first anime, which was (ultimately) No Hugging No Kissing.
 * Similarly, the Nabari no Ou manga has a complete lack of love triangles, so the three main relationships progress at their own paces and pretty much just fall into place.
 * In Eureka Seven, there are seven consistent couples, and the characters involved in these relationship make up most of the main cast. In this story, love is a theme, so these couples are used to make a point.
 * Ryohgo Narita, the author of Baccano and Durarara, really likes this trope. In both series, there are no significant cases of characters competing for romantic affections, all the more remarkable due to Narita's love of putting his main characters in relationships.
 * Namie/Seiji/Mika/ seems pretty significant.

Comic Books

 * The Legion of Super Heroes, from the late 60s to the early 80s. Commonly held to be for an unusual reason. In the 60s, there had been a few stories of the "Adult Legion", showing the team's future. Apparently, in however many years, nobody broke up, and most members got married. (By the usual method, this was one of the first pieces of Fanon "evidence" that Element Lad was gay.) Because DC Comics, or at least the Weisinger-edited titles, had a strict predestination rule in effect at the time, "alternate futures" simply weren't allowed. Eventually - mostly through non-romantic means - that future became implausible, editorial policies changed, and it was reclassified as an alternate timeline. Around the same time, the 1960s relationships started changing.

Fanfic

 * Often occurs in Shipping fanfics. The author's Fan Preferred Couple will at least be on flirting terms by the end of the first chapter and, since romance is inevitably the focus of the story, the fic will quickly become boring due to the lack of Conflict. After a few chapters, the author will get bored with the idealized romance and throw in some contrived drama, usually a Love Triangle formed by the arrival of some hot guy, thus ultimately averting this trope. Oh, whoever shall the heroine (or hero) choose? Expect the new hot guy to turn out to be a cad, but to never quite go away as he's the entire source of conflict.

Literature

 * In the fantasy works of David Eddings, most of the companions have a love match whom they end up with without any serious problems. This is eventually lampshaded at a couple of points, and is implied to happen due to, essentially, divine intervention.
 * And in some cases, quite literal divine intervention, as a particular goddess takes pains to clear up any tangles before they become problematic.
 * Still, it's not like some love isn't unrequited. In The Belgariad, Silk loves a woman he can't have, and Mandorallen practically revels in holding up under the noble love of a woman he can't have -- her husband even approves of their love! -- at least until said husband conveniently dies, leaving the field wide open.
 * Comically, Mandorallen was so prepared to have his love unrequited for his whole life that he has no idea what to do with her, and is very uncomfortable with the entire concept of actively pursuing her.
 * Pretty much the entire world of Xanth. Justified since the land itself apparently likes it that way. In nearly four decades and dozens of books there are two exceptions:
 * The very brief triangle between Bink, Trent and Iris - which was only a "triangle" as much as Iris was openly power hungry and looked to side which ever one of the two men came out on top. A lot has changed in the series since then.
 * The semi-magically enforced triangle between Dolph, Electra and Nada Naga. More info on this can be found under Ascended Fanon.
 * Animorphs. Jake and Cassie like each other, Rachel and Tobias love each other, and fanfiction writers want to believe Marco and Ax are in a relationship. At the end of the series,.

Live Action TV

 * Victorious, although it's still early, out of the 7 main characters, 4 girls, 3 boys, Jade/Beck/Tori is the only real rivalry thus far. The prevalent pairings in the fandom follow this trope to the letter so far, with most of the support going to Tori/Andre, Cat/Robbie as a Beta Couple, and leaving Jade/Beck together. The Les Yay pairings have more support than other Het variations like Tori/Beck, Jade/Andre, Cat/Andre etc.

Theater

 * Loves Labours Lost has four noblemen and four noblewomen, who coincidentally have been in love since before the play started and spend most of the play pretending not to notice each other.

Web Original

 * With most characters comes in couple pairs, and some other single characters gets their lovers later on, this trope is inevitable in Chaos Fighters.
 * Sonichu, a given Sonichu and Rosechu seem to fall for the first member of the other Electric Hedgehog Pokemon species they see that hasn't been thus taken. Played with slightly in that the original Rosechu fell for Sonichu not when she saw him, but when he asked for food, and slightly more so in that it took several more issues after their meeting for Blake to reveal his feelings for Bubbles. This was clearly Christian Weston Chandler's intent for Punchy and Angelica, but changed it due to a request by a fan(they both immediately hook up with the broken halves of the other would-be couple). No conflicts, no problem. (Downright averted for humans and humans that transform into Electric Hedgehog Pokemon.)

Western Animation

 * WITCH does this with very little in-fighting over boys amongst the five main female characters. Will ends up happily with Matt, Cornelia ends up with Caleb, Taranee ends up with Nigel, and Hay Lin ends up with Eric. The only one who isn't definitively paired up by the end of the second season is Irma, and it's heavily implied that she's fond of Martin. The comic series is a bit more complicated, emotions change and real life interferes frequently in the relationships.
 * The Winx Club and the Specialists. You'd think with two groups of attractive teenagers you'd see a lot more romantic trouble, but I guess not. The only complications (besides the usual teen angst) are one-off characters.
 * Interestingly enough, this carries over into WC fanfiction as well, where canon relationships make up a large majority of stories.
 * American Dragon Jake Long where the main romance plot is strictly between the main character and Rose.

Real Life

 * It's become something of a half-joke/half-promise that if you become a Staff Member of Bulbagarden Forums, you're going to meet your soul mate during your service, with no romantic conflict and plenty of support from the other staff. Currently, there are 5 official couples that began while both members served on the staff, with hints of more to come.