I don't live in Japan and get all the info online and in the news. It seems the Japanese are already starting to feel the burden of their aging population. Maybe that's why some there are getting depressed. They already have a low birth rate and so there is increased pressure on the children for caring for their parents. Less siblings you have mean less help financially.
I don't think that ageing is the reason. The Japanese birth rate (1.4 children per woman) is still higher than that in the neighboring nations such as South Korea, Taiwan and Hong Kong. Also, the Japanese life expectancy is much higher, meaning that the death rate is low.