Love Square

The Love Square as a trope is a very specific subgenre of the Love Quadrangle but differentiated in one important point: While in a Love Quadrangle four persons vy for a relationship amongst each other, in the Love Square trope, these four people are really only two people who are in love with each other's (often superhero) alter-egos in a way that does not align, making this trope a beautiful mess of Mutual Pining: Character A is also secretly Character B but loves Character C. Character D is also secretly Character C but loves Character B. Character A/B and Character C/D can thus get rejected by their love interests even though the love is mutual.
A canon love square fandom is Miraculous Ladybug in which this specific modern use of a subgenre has been made popular and spread across other fandoms that have the potential for this kind of setting (such as Sailor Moon for example). Within Miraculous Ladybug, where the heroes don't know each other's identities, Marinette Dupain-Cheng who is also Ladybug is in love with Adrien Agreste (who is also Chat Noir, but which she does not know) but not Chat Noir. Meanwhile Adrien/Chat Noir is in love Ladybug, but not Marinette. This specific setting has created hundreds of canon episodes and thousands of fanworks in which two people unknowingly mutually in love still pine for each other, reject each other for themselves, and create a lot of enjoyable and completely avoidable angst. The most common uses of the trope within the Miraculous fandom attempt to reflect each side of the love square interacting, either as one shots, a series of misunderstandings resulting in an identity reveal, or in an attempt to show overall character growth and the depth of their relationship.
milly-p on Urban Dictionary has described a love square as follows: 
Because of this specific setting, two characters can create four ships/pairings. In the example of Miraculous Ladybug these are Ladrien (Adrien Agreste/Ladybug), Adrienette (Adrien Agreste/Marinette Dupain-Cheng), Ladynoir (Ladybug/Chat Noir) and Marichat (Marinette Dupain-Cheng/Chat Noir). Each ship has different canon and fanon dynamics, very different fan bases and the shippers often interact with each other in a hostile manner even though each ship is made up, essentially, of the same two characters. 
Since the recipe of this trope is made up of exactly two elements (1) Two characters with a secret (often superhero) identity and 2) They don't know the other person's civilian identity) it is easily replicated in other fanworks that include superhero characters and ships, and it has been spreading across different fandoms recently.
==Fanwork Examples==
Miraculous Ladybug
* A Royal Misunderstanding by Chocokuki93 plays with the extremes of this trope by introducing the PV characters (Bridgette and Felix) into the confusion.
Sailor Moon
* In The Unintentional Seduction of Chiba Mamoru by FloraOne, within a Trope Detox, Pining While Fucking, and Teach Seduction setting, Usagi Tsukino who is also Sailor Moon goes to Mamoru Chiba who is also Tuxedo Mask and secretly in love with Usagi, to learn how to seduce Tuxedo Mask because he has shown no interest in Usagi in the past over and over. Within the story, Mamoru despairs over the fact he is teaching the girl he loves to seduce someone else, even though the person in question is actually him, but none of the two know this.
* In Blind by FloraOne Sailor Moon and Tuxedo Mask have a secret relationship with each other while Usagi and Mamoru are close friends. 
* In Idiots by FloraOne Mamoru pines over Usagi for years while Usagi pines over Tuxedo Mask for years.
==Archives & Resources==
Miraculous Ladybug Love Square tag on AO3
==References==
Category:Miraculous Ladybug Tropes & Genres
Category:Sailor Moon
Category:Relationships Glossary
Category:Romance Tropes