When the Third Wheel Strikes Back

When Ye-Seo Jung wakes up one day, he finds himself trapped inside the body of Jesse Venetiaan, the ill-fated second male lead of a mega-hit fantasy romance novel "I Quit My Job, then I Became the Princess Bride." It turns out this second male lead is destined to die at war, trying to protect the male lead. Ye-Seo's goal is to avoid getting entangled with the main characters and survive until the war is over, all while searching for a way to return home safe and sound. But the female lead, Christelle, and the male lead, Cedric, keep approaching him...

(Source: Webtoon Entertainment)