Quick Transmigration: Playing the Supporting Extra in All Kinds of Stories

A male-protagonist quick transmigration story. The protagonist transmigrates into the role of a minor character in novels and other settings, living out a remarkable life in their place. He has no memories in the first two worlds and does some foolish, softhearted things. He gradually changes, then regains his memories in the third world and completes his missions quickly and decisively. Feel free to skip ahead. First world: A hunter in an imperial-examination farming novel.