Two (or more) characters team up to seduce their target together.
An alternate version of this trope can be the two teaming up to put the desired character in a situation which would give either (or both) of them a chance to seduce him/her individually. For example, coming up with the idea to do an activity which needs three people, and then both try to get their beloved alone.
And yet another form of this trope is when the two give each other pointers. Alice points out that if Carol showed off a little more cleavage, she'd look ten times hotter, and Carol admits that if Alice would rein in her bad habits and behave more lady-like, she'd be much easier to approach. Both do their best to cooperate with each other, and then come at their Love Interest with guns blazing. Alternatively, two guys could do the same—as could seducers of two different genders.
The seducers also don't explicitly have to be "rivals". They can merely be two individuals who realize that they have a mutual crush and decide that they stand a better chance trying to seduce him/her together than alone. The target also doesn't have to be someone they're in love with or have feelings for; they could simply be trying to seduce him/her as a means to an end.
There are three typical outcomes to this situation:
- The crush STILL doesn't crack and the wacky hijinks continue.
- They manage to rein the crush in, but their rivalry, or unwillingness to share, ruins things.
- Everybody's happy.
Sometimes overlaps with A Threesome is Manly (a guy wants to do something sexual with another guy, and so includes a girl to make it less "gay").
- In Bleach, this was suggested by the Cloud Cuckoo Lander Orihime, who said that if she and Rukia were both in love with Ichigo (Rukia says she isn't), they could "team up and the girls would win", but this was laughed off as silly...mostly because nobody knew what the hell she was talking about.
- In Please Twins!, Mina and Karen team up for an episode to seduce Maiku in a mistaken attempt to turn him straight.
- In Persona 4: The Animation's adaptation of the King's Game, Rise and Yukiko ensure the game is very lewd and sexual. However, things go a step further, when the protagonist winds up having all three of his potential romantic interests follow the perverse rules to have their own quality time with him (although Chie is clearly embarassed).
- Justified in Strike the Blood. Protagonist Kojou Akatsuki is a vampire whose powers only work if he drinks other peoples' blood, and vampiric bloodlust is akin to actual sexual lust, meaning he has to be turned on to drink blood. So this trope happens twice.
- On one occasion, a familiar turns out to need two peoples' blood to work properly, so when one girl fails to do it alone, the other steps up to the plate as well.
- On the second occasion, this trope is fully invoked, both because a single girl can't arouse the dying Kojou enough to save his life, and because only one of them has blood immune to the Anti-Magic field preventing his powers from awakening. So it takes one girl to restore his powers and the other to slake his thirst.
- Kiss-x-Sis: The Suminoe twins begin the series competing with each other for their stepbrother's affections. But once they discover he's begun dating their homeroom teacher, Ms. Yuuzuki, Ako and Riko set aside their differences and join forces to try to seduce Keita away from her.
- Death March to the Parallel World Rhapsody: Having manipulated her way into being]] Satou's Sex Slave, Arisa attempted this with Lulu when first spending the night with Satou, stripping both herself and Lulu naked in preparation to "service" him. The attempt was foiled by two factors: Lulu was too visibly uncomfortable with being used this way, and Satou wasn't interested in young girls.
- Betty and Veronica of Archie Comics have pulled this trick a few times, usually with both girls ruining it by fighting again. Since the two girls are best friends, though, "threesome" endings are rare but not completely out of the question (in a PG-rated sense, of course).
- Pictured above are the Legion of Super-Heroes members Superboy, Phantom Girl and Triplicate Girl. When Phantom Girl takes an opportunity to steal a kiss from Superboy, Triplicate Girl cuts in using two of her duplicate selves to steal Superboy away and get kisses for themselves.
- In the The Goblin Emperor fanfic Blessings, Csevet and Csethiro team up to seduce Maia.
- There's this Pokémon fic featuring Misty and Serena teaming up to seduce Ash. Contrary to what might seem at first glance, the two girls are actually very good friends and willing to help the other on their weak points.
- Two women in Panic (2000) do this so as to pick up a guy at a bar, though it later seems like it may have been a roundabout way of getting together with each other.
- There was an episode of Gilligan's Island where Ginger and Mary Ann do this to Gilligan.
- Kelly Garrett, Jill Munroe and Sabrina Duncan Charlie's Angels stop short of full-on seduction with Bosley in order to get him to reveal what Charlie Townsend looks like.
- Santana and Brittany seduce and date Finn together in Glee episode "Hell-O", though it plays out as the two girls having a date that they let Finn watch and pay for.
- Attempted by Sarita and Rosita on Eric Young, but his loyalty to ODB made him invulnerable to their charms.
- During the House Of Truth's first Ring of Honor run and at the very start of their second, some combination of Scarlett Bordeaux, Valerie Malone, Kasey Ray, and or Seleziya Sparx, the so called "Hoopla Hotties", would attempt to seduce enemies of the HOT, especially during the matches of Television Title holders Matt Taven and Jay Lethal.
- Aksana and Tamina tried this on Brodus Clay. Unfortunately for them he already had two ladies trailing him. So then they tried to get rid of The Funkadactyls, thinking it would work then.
- In Persona 4, something close to this is what Rise and Yukiko try to pull during the King's Game, when it's Yu's turn to be the King. Both of them make sure that the game is as lewd and perverse as possible, on the off chance that either of them will be picked.
- Subverted in The Witcher 3: Wild Hunt, where the long-standing Love Triangle between Yennefer and Triss ultimately gets resolved. If Geralt tries to romance them both, the two of them both appear to him in their underwear and imply that they're going to have a threesome. They handcuff him to the bed, but then pull out bottles of champagne to congratulate themselves and leave him Chained to a Bed
- In an episode of Gravity Falls, Candy proposes that she and Mabel team up to woo "white whale" Marius, leaving Grenda who eventually wins his heart out of the loop. They don't seem to have a real plan for it and wind up getting in each other's way.