Transmigrated Into a Horror Novel as a Supporting Character

He transmigrates into a horror novel where the male and female leads team up to fight monsters, and he becomes the male lead's loyal sidekick. But he's a coward, and his best friend scares him. To save his own skin, he decides to stay away from the male and female leads and live a normal life. But later, he realizes... Without the male lead, he can't survive, even with his yin-yang eyes... Cue the tears... Male lead, I was wrong... Let me cling to you... Theme: Sweet romance