...why does the title seem to be a complete opposite of the oneshot its apparently a serialization of?
I'm sure there are a lot of changes manga go through before being serialized, the plot/mood were probably some of them. Also, it seems like the oneshot was further into the story, perhaps Matilda has a change of heart towards August later on. It might be very different and it might not be. The most glaring change would be that August already bit Matilda and she didn't become a vampire.
With that aside, I'm so glad that one of my favorite oneshots is a series now