Workplace Story

At my current workplace, people pass by the window right next to the office door and the window in the back room on the west side. Sometimes it's in the afternoon, sometimes in the evening, but a black shadow passes by, so I check if it's a visitor, but of course, there's no one there (￣▽￣;) I always wonder what they're trying to do, wandering around like that (^o^;)