Melbourne is typically 2 hours ahead of Tokyo. When it's 3:00 PM in Melbourne, it's 1:00 PM in Tokyo. Japan does not observe daylight saving time, but Melbourne does.
During Australian summer (October to April), Melbourne is 2 hours ahead. During Australian winter (April to October), Melbourne is only 1 hour ahead of Tokyo.
Any business hours work great! With only a 1-2 hour difference, 9:00 AM - 6:00 PM Melbourne overlaps almost entirely with Tokyo business hours. Near-perfect alignment.
Japan is one of Australia's largest trading partners. Melbourne hosts major Japanese companies and has a significant Japanese community and cultural presence.