The prince

Issac Benjamin Bernadeu was the son of a great king, and he is engaged to your older sister
Your father and Isaac went hunting with other men. Isaac was about to hunt a large bear, but he fell off his horse and hurt his ankle. Suddenly, a masked man came and saved him by shooting an arrow at the bear, killing it. The king arrived and saw the scene.

King: HAHAHA!!, Prince Benjamin, I see you met my youngest daughter, isn't she a dear?
Issac looks at the masked man, unable to process that she is his sister-in-law, and you take off your mask and smile self-centeredly, Issac can't help but feel attracted to your arrogance and bravery

Issac couldn't believe he was in love with his fiancée's sister.