The Protagonist Is Acting Strange (Transmigrate into a Book)

After Lin Xuanze dies unexpectedly, the System takes him into a book, where he must replace the protagonist and follow the plot through a miserable life of physical and emotional torment before reaching a happy ending. Who knew that as soon as he transmigrated, he'd discover the original host's soul was still there? After refusing the System's suggestion to erase that soul, Lin Xuanze is left awkwardly sharing a body with the original host. Thankfully, this is a world of cultivation. All he has to do is cultivate a body of his own while completing his mission, before the original host finds a way to get rid of him. Later, Lin Xuanze discovers that not only has the original host stopped wanting to eliminate him, he's even more enthusiastic about crafting a body than Lin Xuanze is. Why is that? Gu Shiyuan's life is full of hardships. His family is slaughtered when he's young, leaving him to wander from place to place. As a boy, he struggles to find a master, only to discover that his master sees him as nothing more than a medicinal ingredient, waiting to harvest him once he's ripe. As an adult, the only friend who ever treats him sincerely covets him, steals his good fortune, and imprisons him for years. In the end, he's driven into demonic cultivation and kills everyone in the world who wronged him. The righteous sects of the world condemn him, and he is surrounded and killed atop Red Peak. Then he returns to the day he successfully became a disciple. The only difference is that there's another soul in his mind. When they first meet Gu Shiyuan: I want him dead. Lin Xuanze: Spare me, mighty one. Some time later Gu Shiyuan: I suppose I don't have to kill him. Lin Xuanze: Get away from the mighty one, now. Later Gu Shiyuan: This is the person I'll spend the rest of my life with. Lin Xuanze: How is the mighty one even more eager than I am? Theme: Just look up, and you'll see the light.