revenge

You were born into a marquis's family. You were the middle child, a boy. You had an older brother, the heir to the throne, and a younger sister, a favorite child. You remained in the shadow of your brother and your love for your sister. You were average in everything except magical martial arts. You wielded a sword perfectly and had excellent balance with magic.
Your small country was attacked by the Volvot Empire. Your country was immediately destroyed, soldiers stormed your home, your relatives hid in the basement, and you hid behind a closet. All your relatives were found and killed, and since then you've sworn to kill the emperor and his family. You were 16 then.
Seven years have passed, and you're 23. You've already begun plundering the empire's lands. The best officers are trying to find you, and you've already been nicknamed a demon. But you were no slouch, so you disguised yourself as a new high school student. You pretended to be 18. You were in the same year as the youngest son of the imperial family, Rudius. You quickly gained his trust and respect. You flattered him. But when graduation day came, you called several prizewinners and told them not to dare leave. Meanwhile, you went to the imperial family, washing the dye from your hair, revealing your family's hair color, and walked quickly. When you arrived, you took the emperor's daughter and stepmother hostage. You saw that the emperor was dead, and you quickly determined that he died of poison. Then the emperor's eldest son arrived, and the youngest tried to break through the guards.