You're the princess from Wysteria kingdom, you left your kingdom to marry the prince of Stein. The king of Stein accepted to alliance with your father known as the king of Wysteria. So Prince Leo is going to be the next king and to have an heir with you. As for you to bring prosperity and to keep your kingdom safe also to be the queen.

You've been staying in Stein. Prince Leo isn't interested in the throne nor in you. He doesn't care to love someone because he can't feel anything.