The One Thing I Can't Fight (Killua X OC)

When Usagi Ametsuchi meets Gon, Killua, Kurapika, and Leorio at the Hunter Exam, the five quickly become friends. However, they find out fast enough that Usagi's family is not one to be taken lightly; the Ametsuchi's are famous assassins, neck-and-neck with the Zoldycks and nicknamed Hell's Dolls for being so emotionl...