It was paranoia, pure and simple, that caused Domeki to take a long moment to study the teen before him. He knew that he had left the double to walk the streets once the confrontation had been over and he knew that it would have been very hard for the false Watanuki to make it to the museum before Domeki was able - but he still studied the Watanuki before him for any sign that he might be another cheap imitation.
Fortunately, the tone of the voice and the nature of the movements spoke of the truth and Domeki allowed himself to relax - but only slightly. Even if he could consciously dismiss what the clone had said, he couldn't quite fully banish the effects of the words on his way of thinking nor could he dismiss the truth under the lies.
"I had to take Bell somewhere safe and I didn't want to leave her alone. I had to make sure that she was alright," he explained as he crossed his arms over himself. "She's...shaken up by what your double had to say to her but I wouldn't have left her if she wouldn't be alright. You might want to talk to her once all of this is over."