Keiyakukon shita Aite ga Oni Saishou deshita ga, Kono Tabi Saishoushitsu Sennin Hosakan ni Ninmei sareta Jimi Bunkan (Hensouchuu) wa Watashi desu.

In the kingdom where Christine lives, ever since the current king married a commoner, love marriages became highly celebrated. Eventually, a trend emerged where even married individuals wouldn't hesitate to divorce for the sake of "destined love." Exasperated by this view of marriage, Christine meets Leon. To retaliate against her unfaithful fiancé, she lies about finding her "destined love" with Leon and breaks off her engagement, only to discover that Leon is actually the chancellor of the kingdom!?

(Source: Kodansha, translated)