The maps at https://www.atacarnet.com/sites/default/files/documents/airp... and https://www.ana.co.jp/en/jp/guide/prepare/airport-guide/inte... say otherwise.

Immigration (can you enter) --> international baggage claim --> customs (can your stuff enter) --> transfer bag drop.

edit: Same setup for Boston, it seems?

https://www.jal.co.jp/jp/en/inter/airport/bos/info/

Immigration: "Customs declaration form - not required"

Then baggage claim, then...

Customs: "Please show your passport and customs declaration form. (Your customs declaration form will be collected here.) If you have any items to declare, please declare them to an official."