Children, when they must pass the river Sanzu to reach Paradise, must build piles of rocks, because they aren't strong enough to reach paradise by themselves. According to the writings anyway. It is the task of evil demons to kick those piles over, so these children will have to remain in hell. This is why all those Jizō statues exist in this region.
taken on 3 August 2017, 12:25
location: Osorezan in Mutsu, Aomori, Japan