聖女の身代わりとしてやってきた婚約者殿の様子がおかしい

A court magician and a troubled young lady—an arranged marriage love fantasy of fateful substitution! Oswald, the most powerful court magician in the kingdom, lost both his magic and his once-handsome face after protecting his fiancée, the Saint Lily, during a battle against a magical beast. What he received in return was not gratitude, but a one-sided letter of broken engagement—Lily discarded him and sent her younger sister as his new fiancée instead. Her younger sister, Chelsea, was rumored to be constantly mistreated by Lily. Feeling pity, Oswald accepted the arrangement. When Chelsea arrives, she devotes herself earnestly to him, and Oswald finds himself growing fond of her. Yet, it seems Chelsea carries a hidden secret of her own…