26 books • 2 series
Book #3: Hollow Regalia, Vol. 3 (light novel)
Book #4: Hollow Regalia, Vol. 4 (light novel)
Book #1: Strike the Blood, Vol. 1
Book #2: Strike the Blood, Vol. 2
Book #3: Strike the Blood, Vol. 3
Book #4: Strike the Blood, Vol. 4 (light novel)
Book #5: Strike the Blood, Vol. 5 (manga)