Page 13, the handkerchief was still in the pocket.
Page 15, he is gone. Yakou's left hand is behind him.
My guess is he dropped it when he said "I've known you since you were still a child".
Oh boy ... it barely started and already I'm speculating about what's going on. As expected.
@saxifraga No, the goal of the game is know what Yakou is doing when he is behind you. He will perform an action and you have to read what that action might be. Dropping the handkerchief is just the starting example of the game.
Actually I might be wrong on that. It might be as simple as when the handkerchief drop, but I feel like this might be just the first action to predict ? It cant be as simple as to when he dropped it can it ?