After Mistaking the Villain for Someone Else, My Junior Brother Turned Dark

A slow-burn story 『Tsundere kitty × oblivious little mouse』 Sui Yang transmigrates into a cultivation novel aimed at male readers as the great villain's junior sister. The System orders her to win over the villain and save the world, but a System bug makes her mistake someone else for her target. The great villain has a junior fellow disciple who is a heaven-blessed prodigy. Everyone loves to treat the two of them as if they were worlds apart, constantly comparing them. Sui Yang takes the great villain's side, and her relationship with the junior fellow disciple becomes openly hostile. Later, when the sect is destroyed and the great villain and the junior fellow disciple are tied to the city wall, Sui Yang chooses the great villain without hesitation. The young man's bloodstained robe billows in the wind, and his peerlessly beautiful eyes and brows are filled with understanding. Even as he dies, he doesn't look at her once. The great villain successfully ascends, and Sui Yang dies. She thinks she can return to the real world, but the System tells her that the true greatest villain is the junior fellow disciple. By then, he is already halfway corrupted, a demon who massacres cities at the slightest whim. Sui Yang fakes her death and returns, transmigrating into the body of a disposable character who volunteers to heal him because she covets his looks. Before long, the junior fellow disciple will turn this character into a dried corpse and hang her from the city gate. The junior fellow disciple was once the center of everyone's attention. Everyone admired and adored him, but there was one person who wouldn't even spare him a glance. And yet that same person could be gentle and tender toward her senior brother, who was inferior to him in every way. When he was young, he was proud and quick-tempered. They were always parting on bad terms, and when he ignored her, she would get terribly angry with him. Back then, he swore to himself that he would one day draw a clear line between them. But when she truly died, he could only cradle her broken body and stare blankly for a long, long time. That night, the Ten Directions Demonic Realm was slaughtered, and blood flowed like a river. Amid the towering flames of the night, a new Demon King appeared