Later I came to understand that rather than permission to travel, my passport represents my right to return to my home country. Rather than a key to open foreign travel, my passport indicated to other countries where to deport me if need be. Understanding this nuance changed how I thought of my passport. From Japan's perspective, its treaties with foreign countries are a promise to accept me back into the country. From my perspective, no matter the condition, now that I am a citizen, Japan can no longer refuse me re-entry.