Boston is 13 hours behind Osaka

There is no standard 8-to-6 overlap. Someone joins early or late.

Given Boston is 13 hours behind Osaka, the realistic answer is that there's no convenient shared slot during normal business hours. Catch the edges of the day: the last hour for Osaka or the first hour for Boston is usually the least painful option. Because only Boston changes its clocks, the overlap above isn't fixed; expect a one-hour shift when Boston enters or leaves daylight saving.