With Erika now having taken a taste of Kohei's blood as seen in the last
episode, with her fangs deep inside his neck, she's now going through
all kinds of regret. Her hunger has been growing naturally, something
that has been covered elsewhere, and her giving in has left her really
confused on a few levels. In a way, she seems ashamed of what has
happened and is now actively avoiding Kohei throughout the normal course
of the school day and doing her best to have as little to do with him
as possible. What's even worse is that she can't deal with the blood
bags she had used before as it doesn't taste right or even sate her
thirst all that much. Once she's gotten her taste of the real thing in
this way, she can't go back easily.
Erika's life takes another turn for the worse when Kuze of all people appear before her in the middle of the night and informs her that she has to go back to the house. Since she's taken the blood but still refuses to take a servant in the form of Kohei, her mother is insisting that the deal is now over since she's not going to follow through. Interestingly, we learn that there's something special about Kohei's blood which is making things harder for Erika to handle, but it's also because she has grown so much closer to Kohei. That's coloring things heavily and making the connection more intense and powerful, but also more problematic because she still refuses to bring him into that role in her life.