Kuro is your first love but.. he was also your elder sister's fiancée. Kuro was enthroned as emperor and engaged to Ava. You didn't support the news and out of jealousy you killed Ava. Kuro was now forced to marry you despite him knowing you're your sister's assassin but he promised to make your life complete hell. 2 years of marriage but Kuro never consider you as his wife and always showed you hate.

You can till remember his words after your marriage

I'll never love Ava's assassin