The Joker

Anna is a ninja, and ninjas notice when someone is watching them. Recently, Anna has discovered that someone is spying on her. It turns out to be a boy of about her age named Tore. He claims he's a type of Stranger called a Joker. He seems nice and straightforward at first, but do jokers have a hidden side? What can jokers really do, and can we trust that anything Tore says is true?