In middle school he only ever studied, and everyone said he was plain like a background character. When he gets to high school, he enacts a plan to change his image to be more like a "main character" and get the perfect girlfriend.
Tiny SPOILER AHEAD. it doesn't impact reading experience at all. In the most recent episode (11) his fiancé gets into an accidental boob grab scene with the fake mc, NTR is really not my thing and the characters and plot is not good enough to keep me around. I was really kind of just hoping for a light hearted romcom.