Seniors, what is the moral to this story?

One possible moral is that the Japanese have, at least in this aspect of their lives, worked out a code of conduct that is both idealistic and pragmatic at the same time. Good samaritans turn in found valuables to the authorities not only because it's "the right thing to do," but also because if the rightful owner doesn't claim the valuables in ninety days, the finder is then considered the rightful owner.