Exactly. Augustine is gifted with the ability to meld within the darkness itself through Astaroth. That's one of the demon lords most iconic abilities and just like Naoki recognized earlier, neither of them can be detected while in hiding. The realm that lies beyond the shadows is Astarorth's domain. That monster can lie in wait with his master for extended periods of time. This explains why Astaroth doesn't emerge fully.

When Naoki severs Astaroth's many hands, a defeaning howl is heard as near black blood is sprayed across the alleyway like thick paint. The summoner managed to land a terrible blow upon the demon but its master emerges from the shadows behind Naoki with both ornate pistols drawn.

"Silence! I didn't ask for the advice!" He fires in rapid session much like Dante would with his famed Ebony & Ivory. This might be familiar terrority for the summoner since he knows Dante quite well but Augustine's guns pack a bit more punch. They're almost like a musket in design thanks to the explosive cannon-like force of each shot but they're semiautomatic much like current handguns. Unless Naoki wants to be full of lead and blessed silver, he better move!