Before you blame teh mobiluzzz killing consulzz, there are other factors you need to consider because Japan as a country is in decline, failing economy, low birth rates, too many old people, decreasing population.
https://en.wikipedia.org/wiki/Lost_Decade_(Japan)
It is not hard to see why Japanese consume less and less dedicated media, the labor force is going down, not enough children, all these socio economic factors put a strain in the makeup of the Japanese family. Whatever time they've left is spend on a device everyone carries with them.