After Ray's order the group had set off chasing behind Monk towards the fortress. They had some catching up to do and in truth it was unlikely they would get to the fortress before them. Still, the longer they allowed them to investigate on their own, the higher chance they had of finding something and hiding it from Ray and the others.
Ray could have gone ahead of the others using Noir, but with what had just happened, he was worried. He worried that it might have been part of their plan all along. They were still in the shadow continent territory. They had eyes everywhere and probably even knew what they were doing now.
If Ray left these people, there was a chance that was when they would spring an attack up on them. He also didn't want the same incident to happen as before.