Wakiyaku Dakedo Cheat Character Nande, Jinsei Kaete Sashiagemasu!

It's easy to overlook the extras in a novel, but when one avid reader wakes up in the body of "extra" extraordinaire Princess Lyla, she's ready to shed the side character image and step into her mightiest form! Armed with hidden magic more potent than the empire of Belliana has ever seen, Lyla is ditching the palace in favor of a nobler mission--protecting her bias at all costs! Now she must rescue Fian, dreamy descendant of the Kylon Dragon Empire, so he can have his happy ending with the story's heroine. That is, assuming the heroine is still Princess Helene... (Source: Tappytoon) Note: Includes one extra chapter.