Extra C is Secretly Overpowered

It was only last year that I realized that the world I had been reincarnated into was the world of the Romantic Comedy book. What's worse, the person I had reincarnated as was someone featured in the book.A running gag character who the Main Characters ran into at the most random times, of no use, and who would disappear as quickly as he appeared—an Extra C.Last year. A year before starting High School.It was already too late.Extra C had already become...