Hatsukoi wa Marude Yaiba no You ni

From : TCmanga

Satomi was told to marry her brother-in-law, Hongdae. Even since the passing of her sister, Kyoko, Satomi's dad is worrying about not being able to find a successor to the Asahina Private Hospital. In the eye's of Satomi's dad, Hongdae is the best candidate to take over his leadership. In order to prevent protests from the board, he wants Satomi to take her sister's place - to become his wife so that he could once again be related by marriage to Satomi family.

Satomi is just an ordinary gal who studies at a nursing school and wants a first love that she can embrace forever. She is shocked when her dad informs her about marrying Hongdae and gets in a dilemma about it....until one day, she finds something shocking about Hongdae....