The USD/JPY question at the end of WW2 as USD/JPY was priced at 360.00 was how to sustain Japan and ensure viability to JPY. The answer was to price JPY to a correlation degree against the major pairs so to ensure JPY permanently remains a defensive currency pair. Most vital to defense and viability was place JPY as an implant to the majors. An insertion in the correct position ensures JPY survives and trades alongside major pairs but never becomes a leader currency pair. A few examples.
USD/CAD, USD/JPY and USD/CHF. Trading USD/JPY levels,ranges and targets are priced between USD/CHF and USD/CAD.
EUR/USD, EUR/JPY and USD/JPY