A rather more contemporary citizenship question here. I’m looking for a resource for Japanese passport and citizenship rules - do they have birthright citizenship, if a citizen emigrates can they retain dual citizenship, is it different if they emigrated as a child etc.

The Japanese Ministry of Foreign Affairs’ website is very helpful on the subject of visas and emigration for citizens of other countries so I guess I’m looking for a similar kind of FAQ to this - https://www.mofa.go.jp/j_info/visit/visa/ - but for, I guess you’d call it re-emigration? Moving back to the country of your birth as an adult?

Any help, gratefully received!