It's actually happening to most of the East Asian economies. Apparently declining birthrates go hand in hand with economic development.
It's just that Japan, being the first in the region to rev up its economy is also seeing itself as the first to deal with the problem.
That being said, they aren't doing that good a job, and most Japanese companies are already switching gears to deal with the silver consumers (aka old retirees, silver-haired). The native xenophobia means that they can't really absorb enough immigrants to fill the numbers. The farms are already suffering from a lack of manpower these days.
Given that it's a phenomenom not limited to Japan, I would say, nah, the love industry isn't the cause, since other countries don't seem to have as big an industry in that field as Japan.
Would like to comment though, that quite possibly, the sheer strength of the love industry in Japan is due to native culture and circumstances. Each country has certain ideas about sex, family and marriage. In Japan's case, sex isn't as taboo as in the Western worldview. However, the institutions of marriage and family are very heavy. Anyone who has ever watched K-drama would be able to observe the kind of heavy-set role the mother-in-law plays in Korean families. In Japan, that's not exactly the case, but the roles of a husband and a wife are very firmly set. A husband does x ( where x involves working, working hard, for money, to support the family) while the wife is the homemaker (housewife).
First off, can you see how these roles break down a little in today's genderless world? Why can't a wife be the breadwinner? And a househusband? Why not? It's frowned upon somewhat still over there.
Next you see how much pressure it puts on the poor dudes to do well in their career? Japan is like, at one point, the only country surveyed (I think it was out of developed countries) where women don't actually want to climb the career ladder, but simply want to marry well and live as housewives. Factor in the current high costs of living in Japan together with the moribund economy, and you see how guys don't exactly want to get into a serious relationship?
Now, some entrepreneurial Japanese have simply picked upon this market for relations that don't go anywhere. In the culture of Japan where sex isn't as frowned upon, they are able to operate a little more openly than most, and can therefore show themselves as pretty big as compared to more underground operations elsewhere.