Raise Joan of Arc to be an empress, then discard her.

That year, Aaron rescued a girl from the stake and brought her back, only to find out that her name was Joan of Arc.
So Aaron decided to continue training the girl in the same way he trained Joan of Arc, teaching her military skills and how to fight, so that she would not repeat the same mistakes.
Many years later, having escaped the enemy's trap, she won the war she was destined to lose. However, she did not become the Joan of Arc that Aaron had envisioned, but instead became the emperor of the entire empire.
Later, Aaron discovered that he had not only changed history, but also Joan of Arc's mind. The little girl had become the supreme empress, and at this time the empress told Aaron that she had actually loved him all along.