Her Duplicate Luna

Ariana Ferrer served as the King's Concubine assistant in the Arcadia Kingdom. Her parents sent her to work at the palace after celebrating her eighteenth birthday. They cast her out like she's not part of the family.
One night, when Amaya, King Markus' concubine screamed in her bed and died when someone slashed her throat without mercy, they took Ariana from her room and they force her to pledged herself as guilty for killing Amaya. King Markus agreed to put her in the prisoner's cell inside the palace.