Here is a possible solution from EA Answers HQ: "There is an option to turn Yamachan visits off if you click on the staute (there is one in each hood). That will not make him show up in the mountain part at all. He doesn't show up at all anymore then so if you need him for the child festival, make sure to turn him back on."Ughhh I have the same issue! He is annoying. I use MCCC like someone suggested and that fool keeps coming back.