Why Is There a Hidden Plot in the Novel I Wrote?

Gu Can's initial dream was to get into a good university, find a good job after graduation, marry a beautiful and virtuous wife, save some money, build a house in the countryside, rent a piece of land, write novels, grow vegetables, and live the life he longed for. But things are unpredictable. Not long after he graduated from college, he was suddenly diagnosed with terminal cancer. He had survived the most difficult moment of his life, and before he could even begin to feel the beauty of life, he was pronounced dead by the world. After taking his last breath in the hospital's intensive care unit, when he woke up again, Gu Can found that he had traveled through time and space in a novel he wrote, and became the half-brother of the protagonist in the book. He thought that his status as an author would allow him to thrive in this world, until one day he discovered... Why is there a hidden plot in the novel I wrote?