After the Frail Beauty Marries in Her Sister's Place

[Sickly beauty uke x extremely two-faced, scheming seme, probably a short story] The emperor arranges a marriage for the elder sister, but she dreams of wandering the martial world and runs away in the middle of the night. Her family has no choice but to send her younger brother, the uke, who looks just like her but is frail, to take her place until they can find her and switch them back. The uke asks in terror what will happen on their wedding night. His mother tells him to pretend to be ill. After the uke is married off, he never sees the seme, and they live peacefully for a while. Then, two months later, his sister still hasn't been found and sends him a letter, telling him how beautiful the world is and how wonderful it feels to be free. The uke is furious and wants his freedom too. So he climbs over the wall in the middle of the night to escape. After finally making it to the top, he discovers the seme sitting below with a cup of tea in his hand, smiling as he asks, "Where are you going, my beloved consort?" The uke goes stiff with fear and blurts out that he's looking at the moon. But the sky is dark, and the moon hasn't come out. The seme gives him a knowing smile. The uke is so embarrassed he wants to faint, so he simply tells the truth. To his surprise, the seme doesn't react at all. In fact, the seme figured it out long ago but never said anything. He doesn't mind that the uke is a man. On the contrary, he's been in love with him for a long time. The person he wanted to marry was the uke all along. Seeing that the uke still wants to run away, the seme carries him back to their room and says, "Now that we've cleared everything up, let's do what needs to be done." The uke sobs into the quilt, hating his sister for leaving him behind and the seme for bullying him. Theme: Turning a dangerous situation around