When the Vampire Falls in Love

What will happen if Subaru falls in love with a certain human?

After everything was normal, Subaru was being his usual self. Not to mention, everyone in the mansion is also in their usual self. No problems and worries. Everything was fine. Everything was.

One day, Subaru met a certain human girl. Subaru wanted to drink her tasty blood but, for some reason, he doesn't wan't to harm her. But instead, the girl befriended with him. Subaru never mention her around his older brothers even to Yui. He wanted to keep the certain human girl for himself just like Ayato, keeping Yui for himself. But, what if there is a meaning why Subaru wanted to taste her yet he doesn't want to hurt her? Why does Subaru thinks she is important to him dearly?

Pairings:
Subaru x OC
Ayato x Yui
(there could be possibility for the other Sakamaki Brothers to have love interest as well)