I though Kanako was a goddess? Why is she doing a peasant's work?

Whoever that is in the background might answer your question.

Well, there were times when certain royalties even did some dirt work. Although most of the ones that did used to be common folk rather than being born noble.

Even in heaven, the gods still need to train. Planting rice builds discipline, among other things. Mayhap this godling will grow to be a splendid war goddess.

Oh wait.

The artist made reference to Hirose-no-Kawaai, an old place-name associated with Hirose Taisha.
Probably she is Wakaukanome no Mikoto, Shinto goddess of rivers and fertility.