Sure, we're all right with that. We can't put you with the existing groups anymore since those have already been plotted and stuff, but we can put you elsewhere. Let's see... you have the following choices: He could have been with the medics and left in the encampment, he could have joined the Shibusen meisters and weapons in creating the disturbance to flush the enemies out, or he could have been with someone from Shibusen to set up bombs/rescue random unnamed kidnap victims. Oh, the Mairu said it might be okey if Gray also ran into the Katsura/Kuriri/Mairu trio since their log didn’t get far yet (she has to check on it with the other two), so that is also an option if you want to backtag Gray in the mission.