While resting, Zero dreams of his past with Shizuka and their ill father, both of whom were murdered by an armoured figure who he comes to believe was Garo. Waking up in the present, Zero finds Kaoru visiting him but drives her away. Summoned by the Eastern Watchdogs, Zero is ordered by them to support Kouga in sealing a gateway and slaying the 100 Horrors within it. They enter the Demon Realm and eventually destroy the gateway's energy source, but Zero still has his doubts about Garo's part in his step family's murder.
鋼牙の命を狙い続ける魔戒騎士・涼邑零。零のもとに赴いたカオルは、鋼牙と手を組むよう彼に願うが誤魔化されてしまう。拒絶の許されない『黒の指令書』によって、番犬所に呼び出された鋼牙と零は、図らずも三神官より、共闘を言い渡される。百体のホラーを出現させんが為、二頭の魔戒獣が、魔界へと突入する！
