From Lililicious:

"Flowers Dwelling in a Forest Manor," by Yuzuha Seiro, is about two girls who are in the process of being converted to vampires.

There is a tale long ago that a prostitute would cut off her finger to give to her customer to prove she had given her heart to him, or her. Kotone, a servant girl, has fallen in love with Suzuka Ojou-sama and promised her finger to Suzuka. But how will they stay together when Suzuka is to wed someone else?