Usually with a FMC, becoming heroine/support character inside game/novel/series etc. Really fun watching them interact with OGMC.

Story inside a Story inside a Story. No BL/GL. No particular order. 

***Scribblehub:*** 

1. I want a harem but not this kind! 
Cultivator setting, really fun read as MC interacts with various stereotypes of ML. 

***Fanfic that matches:*** 

1. if-i-had-to-be-isekaid-to-a-jrpg-with-harem-cant-i-be-the-harem-protag-instead-of-a-harem
 I didn't know about the series beforehand either, but the quality is really good info about the world naturally came. I didn't even know this was a fanfic in the first place until 30 chapters in, showing how insane it is.