Binkkeopdegi Gongjakbuin

The naïve Yvona is ready to do anything for her amazing fiancé! Summon magical beasts and let him take the glory? Sure! Wreck her body for a powerful spell and die for him? Yes! Watch him secretly embrace her trusted cousin Tristan with passion and deride her openly? Oka— wait. What? Just then, Yvona dies... and wakes up a year in the past with a burdened heart. Armed with her knowledge, Yvona's ready to fight for herself. And hmm, maybe form an alliance with the coldhearted Duke of Azentine...

(Source: Tapas)

Note: Chapter count includes 13 side story chapters.