When you look away for at least a second Sotiris will teleport within a closer radius to you. The entire time you are in the room with him that radius is slowly shrinking and it shrinks fast if you are not looking at him. He emits a 3D looping static sound that get's higher pitch when you're looking in his direction to let you know where he is.
Does he actually have to be on screen in order for it to count as looking at him, or is it okay if you can't see him behind the boxes?
As long as he's in front of you, the boxes won't technically block your sight of him because the programming is very simple.
It seems as though there's a range for him staying in a spot because I walked away staring at him and when I got far enough away he disappeared and moved somewhere else, is this supposed to happen?