S1·E14 Nightmare

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.