I had no idea they were basing protocols on individual U.S. states of departure. Might be useful in convincing my other half not to come back to visit, as my current state has one of the worst per-capita infection rates in the country right now.
https://www.mofa.go.jp/ca/fna/page4e_001053.html - Look at Section 3, Part 2 - It breaks out specific states for the U.S. which is updated regularly to remove/add states based on local cases reported in that region.
Currently: States of Idaho, Arkansas, Arizona, Oregon, Kentucky, Colorado, Nevada, Mississippi, Montana, Louisiana, Washington
And then you'll see releases/changes such as: (All cross border travelers and returnees from Estonia, Nigeria, France,
States of Kansas, Delaware, Maine (United States of America) arriving after 0:00 am (JST) on July 9, 2021, are not subject to the above mentioned quarantine measures , but until that time, the quarantine measures for border enforcement as mentioned in (iii) above shall be applied.) [This means that they go back to the 14 day rule at home instead of the 3 day forced hotel stay, etc.]
Currently also listed:
States of Utah, Wyoming
States of Oklahoma, Missouri
States of Indiana, Kansas, Texas
States of Alaska, South Carolina, Tennessee, Nebraska
State of Florida
It's important to note that this is for where you stayed at - not where you transited through. They ask specific what location you were 'staying' in and not about where you transited through to get to Japan.