Well I for one encourage you to write more on this. I can't believe that this crossover isn't done more often.

The idea of Alucard Meeting the Scarlets is not bad but a few things are of

First of the touhouverse is strongly based on Myths and such. it is claimed by Remilia that she is a Descendant from Tepes so we have there the connection. The name Scarlet is probably a creation of Remilia herself. She is known to be very full of herself and renaming herself in such manner would be very much like herself.

Another point is don't praise Alucard to high Yes he is Strong but saying he would be so much stronger than other touhou character ? no definitely not on par But the strength of a Yokai comes with age and he is only 600 years old there are other far older far stronger Yokai in Touhou. And his Armor is shown in the Manga/Anime it is just an Armor nothing demonic or such saying such things is silly again.

Don't use Japanese weapons in an European setting it is uncreative and shows how little you use Wikipedia and research things.

The OC it is clear that you needed an oc for the scarlet sisters i give you that but stating he is on par with Dracula and even giving him the Name Vlad ? be a little more creative.

That are my thoughts on what you have written if you have questions or want to reply just write back.

I hope Alucard teases Remilia relentlessly.

So... Is the one in red Vlad Tepes (the father of Remilia and Flandre) and the one in armor Dracula (who will be later known as Alucard)? Or is it the other way around?