I like your style of writing so far, and also that you put in the "running gag" about Claire causing outbreaks wherever she goes. I don't have anything to complain about but two minor issues:
Firstly, leave out the "years old", and secondly, most people don't grow anymore at that age. He wouldn't be any taller or broader at 25, so judging his age by the size and physique doesn't make sense in this case. It would if he was about five years younger.
Then, you and I have a disease in common: the MSS, also known as Monster Sentence Syndrome. Look at this:
That's just one too long sentence. A few breathing pauses now and then would make it more comfortable to read, like for example:
Claire followed the man to a wide marble lobby which seemed to contrast the very modern glass exterior of the building. Full stop. Two elevators were placed on each side of the room. Full stop. He swiped his card on one of the readers and the door to the elevator on the other side of the room slid open. Full stop.
"That's an inconvenience", Claire thought. Full stop.
They both walked back across the room towards the open doors.
But other than that, I like what I read so far, and I'm now "following" your story on fanfiction.net to see what you will make of it.