The country should be more open and actively incentivize immigration, clearly the Japanese population is not interested in reproducing anymore, which is causing the demographic bomb where the old people will not have an income source of anyone to take care of them, no matter how many robots they build, so be more welcome to young outsiders, specially young couples and families with young kids, give them language courses, cultural adaptation lessons and some money to sweeten the deal, that will help, just don't make the mistake of bringing young single men, that will be worse in every way.