Japan will likely embrace and enhance nanomedicine (as it's already doing with robotics) for keeping segments of its aging population from drawing on employable younger people for aged-care services, and maybe to keep some of the aged population employable for longer, in order to avoid 外国人 immigration to deal with the low birth rate and labor shortages.
China, on the other hand, will develop nanomedicine to keep high-ranking octogenarian or nonagenarian communist-party officials alive and well enough to stay in power.
I am assuming that returning issei and nisei immigrants would not be unwelcome. Japan's immigration policies are predicated on a sense of ethnic superiority and reflect the attitudes of many Japanese. My remarks were ironic only to the extent that they were hyperbolic.
1. Nanobots: Science fiction and comic books say you can build nanobots to cure deadly diseases. Sure, these robots are still a long way away, but they are being built up, one component at a time.
2. Nano-sensors: The reason why nanoscience is so fascinating is that materials behave differently when you scale down to the nanoscale. For instance, a material you have might be diamagnetic (non-magnetic) in its bulk form, but the moment you make nanoparticles of the same material, they become paramagnetic[1]. These properties help design effective and efficient sensors for gas leakage, nuclear radiation, fault/fissure detection, mechanical stress detection, seismographs, etc.