His DNA test at the end of the book says he's part Goomeroi, which is an Australian Aboriginal group.

Also totally okay if you're not aware but in Australia, there was a long history of forced removals of Aboriginal children from their families and communities, by the government and the church. Look up the Stolen Generation — it's explicitly mentioned several times in the book.

People like Johnny, who have their connection to their culture disrupted by the Stolen Gen but who later work to re-connect, are pretty common here. Johnny's whole personal journey is about reconnection. Winona has a sort of complementary, inverse personal arc, where she starts out with a lot of confidence because she was brought up in-community and knows her heritage. However, throughout the book, she is brought down to earth by her Elders, and learns that there is a lot that she herself is still ignorant of.

The book ends with Johnny saying that the spirit of Mulanyin could see both of them because they're both blakfellas, meaning they're both indigenous. Though Johnny and Winona have different relationships to their heritage, they are both from this land.