Marrying a Doctor's Concubine on His Behalf: the Sickly Prince Is Just Pretending

You seek justice in the country, and I protect the hearts of the people. We stand side by side and have no fear in the world. It's a sweet counter-convention of two-way substitute marriage: the heroine marries the sick man for his sister-in-law, and the hero marries the sick man for his concubine. As a result, the two "stand-ins" discover on their wedding night that the other person is actually their true sweetheart.