Broke off with the Nether King, the Saintess Regrets Madly

"Hades, the God of the Underworld, poured all his divine power and riches into nurturing Aurora, Saintess of the Light Temple, for eighteen years. On her coming-of-age ceremony, she publicly broke off their engagement to marry the king instead.
Celia, her twin sister who had been bullied by Aurora for years, is the true reincarnation of the Queen of the Underworld. She reunites and recognizes Hades, awakens her divine powers, and joins forces with him to slay the Demon King Lucifer. As for Aurora, she falls into darkness and corruption, eventually turning to ashes."