Backpack means the baggage to carry on the back. Today's Japanese often carry them in front of their body. Especially in the train and in the station.
Carrying backpack in the back cause pushing and stinging the person in their back, so, recently Japanese stop this behavior.
But on the contrary, Japanese carry their backpack in their front.
The pushing and stinging still remain to the person in front.
In front, noticing the harrasment may be easier, but very little Japanese notice it.
In Japan, train riding will be disappointing.