Shindemo Oshimasu!!: Jinsei Nidome no Koushaku Reijou, Kondo wa Dansou Kishi ni Natte, Saioshi Kon'yakusha o Osukui Shimasu

Serena is a duke's daughter who was engaged to Finis, the leader of the pride of the empire, the Black Wolves Knights Order. Ever since she first saw his portrait, she became infatuated with him and has been fangirling over him with feverish fervor. But just as their wedding day was drawing close, the two of them were suddenly murdered by an unknown culprit.

By the time she realizes it, her "second life" had already started with memories of her past life still in tact. Determined not to let Finis die this time, Serena joined the knights order so she can protect her number one favorite Finis as a knight herself!

(Source: Kodansha, translated)