My Magical Rival is My Future Husband

When Ava Piper returns from ten years in the future and announces that her brother Harvey will marry his old magical-school rival Darian Malvern, nobody believes her. Then she exposes Harvey's cheating fiance, and Harvey accepts a one-year contract marriage with Darian to enter the Malvern archives. Cohabitation, family dinners, workplace gossip and one stubborn tattoo gradually reveal that the marriage may be contractual, but Darian's love has never been.