Yoake no Vampire

From Mangaupdates:
Manga adaptation of the work by Anne Rice. It was later renamed as Interview with (the) Vampire.

Louis and Lestat are two vampires living in the 1700s who have a platonic love/hate relationship. Louis is about to leave Lestat but suddenly Lestat turns a little girl (Claudia) into a vampire and Louis can't leave her...But what happens when Claudia's mind matures but her body stays the same.