My Destiny Supporting Role

Jiang Lai is a senior cosplayer. One time when he was cosplaying Spider-Man, he was traveling between buildings and found that he had no spider silk and ended up traveling through time. When he came to this new world full of all kinds of weird things, he discovered that this world was a book written by a stupid author, and he was just a supporting character. The good news was that he was not cannon fodder, and the bad news was that the protagonist was lost. If the plot could not get back on track and the stupid author cut the book, he would also end, so he embarked on the road to find the protagonist, but... Why are there so many people who look like the protagonist? Who is the protagonist?