The opening is the Gremory group hunting a stray devil named Maverick. After sending him to stand trial in the Underworld it’s discovered that he was working in a lab developing Chimeras. The next day while Issei is wondering about Maverick’s parting words, he overhears how many of the school girls are getting sick with anemia and that all the victims possess the same characteristic. Finding the source of the illness, Issei wants to protect it upon finding out its special ability. However, the rest of the group disapproves strongly, especially as some of the members are about to be inflicted with the same illness.