Fortune Arterial: Akai Yakusoku

Synopsis

Erika has a dream where she sucks Kohei's blood. There are rumors of a vampire at school, but both Iori and Erika deny it being them. Both Kohei and Erika try to look for that vampire at night when they meet up with Iori and Seichiro. The four of them then see a vampire. It is revealed she is Kuze who is a servant which serves vampires. While they chase Kuze, Erika meets Haruna(in her vampire mode). And it is finally revealed that when the accident happened it was Erika who saved Haruna and erased her memory. Because Haruna saw her in Vampire mode, Iori suggested she should erase her memory like before. But Kohei begs Erika not to do that but Erika refuses meanwhile Haruna awakens and thanks Erika for saving her six year ago. Erika proceeds and instead of erase her memory, she restores them all.

(Source: Wikipedia)