A kukuri born with the Ethereal Mutation can learn one magic type from the moment they are born. This means, regardless of rank, you can use magic training right from upload.

The second magic element is only unlocked after the kuku reaches arisen, as it would be with a normal kuku.

The two different magic types can be entirely seperate elements (i.e Fire and water). Or it can be the same element, but different refined magic (i.e Magma and inferno from fire).

Your kukuri must complete training for both chosen elements. This means if you choose two entirely different magic elements (Water and Fire for example), you will need to complete 4 trainings to reach refined magic for both (2 basic and 2 refined). If you choose the same element with two different refined skills, it will take 3 trainings (1 basic and 2 refined).

Your kukuri may show both elements on their import upon the training for each being completed.