Heukwahan Noyenameul Gildeuryeotda

Arlenne Serkia is granted the chance to go back in time and devises a plan to ruin the man who stabbed her heart. The key to her scheme is the slave Kasadin, renowned for his unmatched swordsmanship and stunning beauty, whom she adopts as her "younger brother" to use as both her sword and shield. But Kasadin has a past much deeper and more dangerous than she realizes... and this drives his own motives for staying close to her, both personal and political. If Arlenne isn't careful, the user might end up being used!

(Source: Tappytoon)