Much has been made in the media over the problem of Japan’s aging population and shrinking workforce. But there is another demographic time bomb, at the heart of Japan’s most militantly youthful sector of society, just waiting to explode.

I’m talking, of course, about the boom in Japan’s idol population. Yasushi Akimoto’s mass idol factory alone supports more than 300 young girls through the likes of AKB48, SKE48, NMB48, HKT48, SDN48 and Sony marketing item Nogizaka46, all rushing headlong into “graduation” by their mid-20s. Is Japan ready to cope with such an influx of unemployed young women with a very specific skill set?

Years ago, there were a number of career options available to a young singer past her “idoling” prime. The first and probably most common was to simply marry her producer, manager or older male drama costar, then drop off the map. AKB48 supremo Akimoto is himself married to one of his former stars, Mamiko Takai of 1980s mass-idol-group pioneers Onyanko Club. But unless he’s planning a rapid conversion to old-school Mormonism, that option isn’t open to the remainder of his current charges.

If any of them want to remain in showbiz, there is always the option of becoming a TV presenter, a transition that ’70s idol Ikue Sakakibara managed relatively gracefully. The problem with this approach is that TV channels in Japan aren’t multiplying at anything like the speed they would need to keep up with the idol population.

An acting career could be another route, with both Ran Ito and Yoshiko (Sue) Tanaka of ’70s idol trio the Candies carving out successful screen careers; panty-flashing ’80s idol Kyoko Koizumi also proved to be a genuinely talented, multi-award-winning actress. Ryoko Hirosue is now far better-known for her roles in films such as the Academy Award-winning “Departures” than she is for her ’90s bubblegum pop confections such as “Maji de Koi Suru 5-byo Mae” and “Daisuki!”

If the TV or film-festival route proves too difficult, there is also the path taken by ex-AKB48 star Rina Nakanishi, who in 2010 changed her name to Rico Yamaguchi and leaped into the world of pornography.

Modeling can also provide steady work for an ex-idol into her 30s, although the ridicule that greeted AKB48’s diminutive Tomomi Itano when she was photographed alongside a group of typically svelte, long-legged Samantha Thavasa models suggests that the idol body is not quite suited to the modeling world’s harsh expectations.

Ideally, though, many idols would surely prefer to prolong their singing career, and the undoubted queen in this regard is Seiko Matsuda, often dubbed “the forever idol.” Matsuda has her own iron determination and will to succeed to thank for this. Her refusal to quit and settle down even after getting married and having children was a scandal in its time, but Matsuda rode it out and forced a change in social attitudes. The knack for self-promotion that saw her, the former Noriko Kamachi, choose a stage name combining two of Japan’s hottest commercial brands undoubtedly helped.

Matsuda was also aided by the fact that she can actually sing. If an idol is to continue making music into the fullness of womanhood, it’s essential that her music matures with her. Bubble-gum idol Aya Matsuura’s career was cut short by serious health problems, but she continues to perform occasional shows, primarily in jazz clubs. A form of smooth, jazz-tinged balladry seems to be the musical model of choice for idols seeking to mature, with the aforementioned Kyoko Koizumi also having pursued a more jazz-influenced direction in much of her sporadic post-’90s music.

With the mainstream of grown-up Japanese pop atrophying at an alarming rate and clearly unable to accommodate a flood of newcomers from the idol world, perhaps the safest path is to seek out a musical niche with a steady audience.

Maybe what’s needed is a kind of system of counselors tasked with guiding former idols back into society, rather like probation officers helping newly released prisoners. Or perhaps a kind of G.I. Bill that provides training and apprenticeships to recently demobilized popstrels. In any case, we can only hope that when idols can no longer be idols, they are at least not left to become idle.