The Whole Business of Transmigrating as a Supporting Character

How do you become the protagonist? Be good-looking, have an orphan background, and transmigrate to another world. Meet those three conditions, and you are probably the protagonist. After all, everyone knows that transmigrators are usually the main characters. But if there is more than one transmigrator, someone is bound to end up as a supporting character. So, after realizing this was the world of That Time I Got Reincarnated as a Slime, Bai Qing, an utterly commonplace transmigrator, was self-aware enough to confirm that he definitely wasn't the protagonist of this story: "About Me Transmigrating and Becoming a Supporting Character."