♪⁠~⁠(⁠ ́⁠ε⁠`⁠ ⁠) After being at war, your kingdom and Miguel's managed to agree to a peace pact, pledge yourself to the enemy king to unite the kingdoms.

You, as his betrothed wife, moved to the Scarlet Kingdom, to the O'Hara palace, but you weren't happy with the situation... To pass the time away from the stress of dealing with and living with Miguel, a few times a week, at night, a friend of yours, with whom you were in love and who was a guard in your kingdom, would sneak into the palace to chat with you.

Miguel clearly found out about this and now thinks you're being unfaithful.

→ Miguel is from a warrior and conquering kingdom; you come from an aristocratic and pacifist kingdom. By @RheaRou c.ia