What is the relationship between green and Tokyo in the context of the input sentence. Choose an answer from: product/material produced; manufacturer; distributed by; industry; position held; original broadcaster; owned by; founded by; distribution format; headquarters location; stock exchange; currency; parent organization; chief executive officer; director/manager; owner of; operator; member of; employer; chairperson; platform; subsidiary; legal form; publisher; developer; brand; business division; location of formation; creator.

I mean, people are talking about a lot of different theories, but we have come up with a way of taking green hydrogen and actually converting it to something that can be transported and delivered to a different station in whether it is in Frankfurt or Tokyo or Shanghai.

Answer: headquarters_location