My Dad Married into a New Family, and I Got Five Immortal Sisters

[No saintly heroine, urban superpowers, sweet romance, black-haired male lead early on and white-haired later] Tian Yuan always thought he was a transmigrator born with a System. His birth mother died giving birth to him, and his father disappeared when he was five. After twelve years of a miserable life, he learns that his father married into a wealthy family. After a short time living there, the System reveals the truth about the world. To protect his family, he sets out on the path of a guardian. Can he keep his family and the woman he loves safe?