I can see why this carries the comedy tag. Honestly, Atsushi should just call the cops and tell himself that Masa was never much of a friend anyway. If he did that, he would face no criminal charges whatsoever. But if he doesn't do anything, he's actually helping a kidnapper.
Though that being said, there's something fishy about this whole deal. I almost expect there to be a hidden camera and Atsushi was just pranked heavily.