Comment by Strategemini
This is a Self-Insertion, but it's not a Mary Sue fic. It takes Sailor Moon and makes everything Darker And Grittier. There are elements of several other series mixed in as well, all of which are done in a way that makes perfect sense. One of the longer Sailor Moon stories out there, Gaijin is excellently characterized and the plot keeps you guessing. Definitely worth a read.