Lexus realized why he had a bad feeling about meeting her friends. They were interrogating him like some kind of criminal. They had a lot of questions that would have been normally considered rude and too blunt.
If they weren't Anna's friends he would have shut them up already. But they were people who cared about Anna. They were wary of him for her sake and he was glad that she had friends like that.
They were also people whom Anna trusted. Thus, Lexus had to bear with their wariness until he could convince them that he wasn't out to hurt Anna.
But the more questions they asked, the faster he felt his energy getting drained as he answered all of them as best he could. He stopped himself from flinching every time they asked something he didn't like.