Transmigrated as the Second Male Lead's Twin Brother [BL Harem]

My younger sister was an avid reader of romance novels. On her birthday, she begged me to read a novel named, "The Dark Catastrophe: The Holy Saintess Saves the World." What I didn't expect was that after reading the novel, I would get hit by a truck and die! When I woke up, I found out that I transmigrated as the second male lead's younger twin brother, Cash Reran! Cash was the second-born son of Duke Reran. To make matters worse, Cash Reran has a terminal illness and was fated to die in the first chapter of the novel! Although he was only mentioned during the first sentence of the novel, he played a very crucial role. He was the sole reason for the novel to exist because the novel plot only began after Cash dies from a mysterious illness. After being transmigrated a year before the novel's main plot, I decided to be a lazy bum and watch things from the sidelines. During my observations, I found out the villainess is a shy and misunderstood girl while the heroine is actually a green tea bitch. Furthermore, how come I didn't even do anything yet the main characters of the novel are always following me wanting my attention!? It seems like I somehow changed the novel's genre from straight romance to BL!!! [Short Chapters]