Himea is a vampire with great powers and when she meets Taito, she falls in love with him. She puts a curse on him so that he will always be with her, but she is abducted by a strange boy and Taito loses the memories of their encounter for some years due to a spell. Himea fell for Taito, because he was the only one who didn't want her because of her vampire powers. This was probably because Taito didn't know that Himea is a vampire.

Taito has been really sleepy lately, and keeps dreaming of a female vampire who says she has given him her "poison." Sometimes he even thinks he hears her voice when he's awake. But after surviving an accident that should have killed him, Taito's world changes drastically and he realizes that his dreams are more real than he thought.

According to the official website, an OVA of Itsuka Tenma no Kuro Usagi was announced to be bundled with the ninth volume of the novel. 
An animated crossover between Itsu-Ten and The Legend of the Legendary Heroes (Densetsu no Yuusha no Densetsu or DenYuuDen) fantasy story.

Picture Dramas from the Blu-Ray disks. 
Episodes: 
1 - Let's Just Do It Radio! 
2 - Each One's Breakfast 
3 - Himea's Guitar Lesson 
4 - Each One's Bath Time 
5 - Traditional Feeling 
6 - Izumi-chan's What If Series

A freshman of Miyasaka High, Kurogane Taito was average at everything. And all this while, he had believed himself to be an ordinary regular guy. But, he was wrong. The reason was because of a certain event 9 years ago. For the sake of a promise he had made then, he had already stopped being ordinary a long time ago. However, not a single fragment of his memory about that promise remained. Who had stolen his memory and to what ends? One day, as a consequence of a certain event that had descended upon his ordinary life, his memories were restored. That marked the beginning of his &ldquo;extraordinary&rdquo; life... 
--- you&rsquo;ve finally died. I&rsquo;ve been long waiting for this day --- 
I&rsquo;ve always thought that I&rsquo;m a supporting character in life. 
But once again, it starts from here. 
My story. 
I&rsquo;ll &ldquo;die 7 times&rdquo; for your sake 
Everything starts from that promise. A story of a reverse school fantasy! 
(Source: Baka-Tsuki)

Taito has been really sleepy lately, and keeps dreaming of a particular vampire who says she has given him her "poison". Sometimes he even thinks he hallucinates her voice when he's awake. But after surviving an accident that should have killed him, Taito's world changes drastically and he realizes that his dreams are more real than he thought.

Himea Saito