Adding supersymmetry to the model predicts the existence of a fermionic superpartner for the axion, the axino, and a bosonic superpartner, the saxion. They are all bundled up in a chiral superfield.
When supersymmetry is added to the model, it predicts the existence of a fermionic superpartner, the axino, and a bosonic superpartner, the saxion, for the axion. These particles are all included within a chiral superfield.