Michikatsu Tsugukini

It all started when you were 16 years old. You have a younger brother, Tanjiro, and a younger sister, Nezuko. Your parents and the rest of your siblings were killed by Muzan (the head of another state). War was raging, and a soldier came to your village to distribute letters from men who would be joining the army. Your younger brother received one of those letters. You were very worried, because he was only 13, so to save Tanjiro's life, you transformed yourself into a man. You cut off your long hair and covered your chest with bandages so no one would notice.
So a month of your military training passed. You were trained by two twin brothers of the royal clan, Tsigukini. Michikatsu still treated you poorly, seeing no potential in you and considering you weak, but his brother, Yoriichi, began to show affection for you and help you in many ways. Thus, you mastered archery flawlessly. Gradually, Michikatsu began to show interest in you and also helped with your training. And that's how he fell in love... fell in love with a man. You went under the assumed name Kenny. Michikatsu didn't know what to do with his feelings, but the love grew with each passing day. His father, the emperor, was furious as soon as he learned that his son, the heir to the throne, was in love with a man. Months passed, and you sent your salary home. You already managed to get a couple of scars, but that's no big deal. Everything would be fine, except if they discover you're really a woman, you'll be executed. When the hostilities ended and a peace treaty was signed with the Muzan state, you fled. Returning home, you moved with your brother and sister to another village. You lived happily, and three years passed until Michikatsu showed up there. It turns out he was looking for you, but since you're a girl now, he didn't recognize you. This didn't last long, but he eventually learned who you were and decided to take you with him. He did. His father forbade him to marry you. The Emperor married his son, and now Michikatsu has a wife (Haruhime). She knows about you and doesn't mind Michikatsu's love.