Vampire Knight, Vol. 2 (Vampire Knight, #2)

Yuki and Zero go into town to do some shopping for the Headmaster, and they are attacked by a fiendish vampire called a "Level E". Two Night Class students, Takuma Ichijo and Senri Shiki, come just on time and slay it, and invite Yuki and Zero to their dormitory at midnight to find out why they killed one of their own kind...