Shinitagari Reijou wa Kyuuketsuki ni Dekiai sareru

A love so deep it feels like drowning, bestowed by a beautiful vampire upon a young lady who wishes for death. Earl’s daughter Adele Welch was neglected by her parents and even had her fiancé stolen by her younger sister. Feeling utter despair and intended to end her life in solitude, Adele is interrupted… "If you're going to die anyway, won't you give that life to me?" The one who saved the unfortunate Adele’s life was Fee, a beautiful vampire from a ducal house. Chosen by Fee, Adele resolves to leave her family home behind. Though bewildered by the sweet affection poured upon her daily, Adele begins to find happiness by his side.

https://www.cmoa.jp/title/317884/