Fake is a 20-chapter Maria-sama ga Miteru fanfic written in 2006 by Vega62a. It can be read here (or incomplete on Archive of Our Own here). Fake is more-so based on the manga adaptation than the anime or original light novels, but all three are similar so reading the manga isn't needed to understand the story.
Now that Sachiko has graduated Lllian, it's only time before she is married off to her cousin. The marriage looms over her and it feels as if she's become a prisoner in her own home. Sachiko is uncomfortable with the marriage for multiple reasons: Suguru doesn't love her like that, she doesn't like being forced into being someone's trophy wife, she doesn't want to get married yet, and she has her own conflicting feelings towards her best friend Yumi.
Fake provides examples of:
- Adaptational Angst Upgrade: Sachiko is depicted as more sullen and troubled than in canon. She also suffers from a lot of internalized hatred.
- Continuation: The story is set post-series after Sachiko has graduated.
- Dark Fic: The tone is darker and more mature than the relatively lighthearted source. Sachiko is very bitter and depressed about her life.
- Homophobic Hate Crime: Downplayed. Kiyomi and Satoi mention that they suffered a lot of homophobic bullying and ostracism while going to Catholic school.
- Kissing Under the Influence: Yumi and Sachiko have their first kiss while drunk after a party.
- The Mistress: This is discussed in the first chapter due to the fact Sachiko is marrying a gay man. She guesses that Suguru will have his own lover, but wonders who will be her own. Sei is her first option for a mistress. Not because of the sex (Youko would be better for just that), but because she would kindly reject her advances.
- Slash Fic: The main focus of the story is how Sachiko's Arranged Marriage affects her relationship with Yumi.
- Title Drop: The title refers to Sachiko feeling fake. She drops the title in a conversation with Yumi:Yumi: "That's silly, though. What else would you be?"Sachiko: "A fake."
- Trophy Child: Sachiko's parents are more concerned with image than her own opinions and mental well-being.
- Trophy Wife: Marrying Suguru would turn Sachiko into this. She's not keen on being just his trophy wife, so she's going to university to get a higher education.