Gu Yuanluo, Legitimate Daughter of a Military Family

[Historical romance + two powerful leads + the whole family dotes on her + the second female lead has a System] Let me tell you a secret: I was born into another world as Gu Yuanluo, the daughter of a military family, after coming from the modern world. How I ended up here is a long story, so I'll keep it brief: it was because of my best friend's ex-boyfriend... After an accident, Jun Hewang was badly injured and, by a twist of fate, ended up in the general's residence. He was rescued by the general's second legitimate daughter, who had just returned from the frontier, and the two became entangled from then on. Jun Hewang needed a princess consort, while Gu Yuanluo needed a powerful ally. So she struck a deal with Jun Hewang, the second prince of Guangxia: they would sign a contract and pretend to be husband and wife. The general's family had too many enemies and needed someone to back them up. Gu Yuanluo: “Jun Hewang, I may not be able to fulfill our agreement for now. I'm a daughter of the Gu family, born into a military clan. When someone puts their trust in me, I have to fulfill my family's duty. If I make it back alive, I'll marry you. If I don't, I wish you a peaceful and happy life.” Jun Hewang: “I'll wait for you to come back. Don't worry, you won't be at the frontier for long. I'll come and get you.” But Gu Yuanluo discovers that her best friend seems to have transmigrated here too. She just doesn't know why her friend refuses to acknowledge her. Though she doesn't know the reason, Gu Yuanluo believes her friend must have her own difficulties. (The second female lead, Jun Siwan, reached the peak of her guilt. The Main System found her and randomly assigned her to one of the three thousand worlds, where she must win over Gu Cangming. Once his affection reaches 100, the mission will be complete, and she can save the person who is gravely injured and on the verge of death. If she fails, she will be erased.)