The Cold Husband Is Very Affectionate

Why did the contract we agreed to last for three months turn into a lifetime contract? And also want to be his wife? She was just an ordinary girl, but she met him by accident and became the treasure of his heart. He was aloof, domineering, ruthless and cruel, decisive in killing, and extremely domineering, but he doted on her to the core. (The male and female protagonists are clean physically and mentally, 1V1, doting article.)