The Swapped Bride: He Lost Me, Then Everything

Elf princess Sera has been betrothed to noble Kael for seven years, yet every Star Festival, she draws the losing lot, becoming the clan's laughingstock. In year eight, she overhears the truth: Kael cheats with white lots to keep her ashore while his mistress boards the ship each year. Heartbroken, she awakens. At the drawing ceremony, Sera publicly draws the red lot and boards the magnificent flower ship of allied prince Rion, marrying into a higher house. Kael's cheating is exposed; the king dissolves the engagement. Sera ascends as the new queen, and with Rion, brings the traitorous Kael to justice, becoming the elf queen who guards her homeland.