I don't believe in ghosts and spirits. There's no real scientific explanation for it. Many stories of demons, ghosts, spirits, angels and etc. are used to teach people proper moral conducts. I do not believe that they truly exist. It's true that at many times you'll feel the presense of someone watching you, but a lot of that is created by psycological factors. And like Ero_Ni_Sama said, it could be a hidden camera or something.
Proud and loyal Co-owner of the Konoha 5 FC