I would totally get that if the virus was in Japan and not the UK, or vice versa; but it's already in both places. If I go, I might catch/spread it in Kyoto; but if I stay, I might catch/spread it in Bristol (unless the government orders an Italy-style lockdown - as they may well). If there were a marked imbalance between the two places in terms of the prevalence of the disease that would certainly be different, but that's something it's hard to know several weeks out. It's a very fast-changing situation!