Not Japanese, but usually a solution is to promote immigration, especially in the short term to fill an increased demand for healthcare staff. That's probably the most obvious answer, but looking at why there is a decrease in children being born to level out the aging population, such as a lack of work-life balance, an increase in depression being diagnosed , economic hardship/feeling that in order to be able to provide you have to reach unattainable financial goals might be behind this concern. This likely hasn't been of much help though as it's just a foreign perspective.
Usually when there is a lull in the available working age population, immigration is promoted, as in to have either people from other countries come over to work or to promote internal migration to areas of concern (rural areas might be lacking teachers, medics etc). This is still is still a short term solution that only really deals with the issue of an ageing population in terms of more demanding jobs not being fulfilled though, I remember reading a while back, that a consequence of an older workforce meant a resistance to adopt new technology, hence why fax machine are still so common for example. I don't know what the attitude is to migration in Japan, be it from citizens or the government, so maybe someone can be of help, and has a personal insight into this?
Japan is considered to be at stage 5 in the demographic transition, meaning its natural increase rate is negative (more deaths than births & aging population). If you search up "Japan stage 5 DTM" or "stage 5 DTM countries", you should get a lot of information about this and solutions some propose. Like @ clouds mentioned, immigration is what keeps countries in stage 5 of the DTM stable. Germany is a good example of a country in stage 5, yet also has high immigration rates. Hope this helps xoxo
Have you heard anything about the dangerously aging population in your country and if the government plans to take some metres to help balance the situation and what those metres may be?