The requirement of electroweak naturalness in simple supersymmetric models implies the existence of a cluster of four light Higgsinos with a mass ∼100-300 GeV, the lighter the better. While such light compressed spectra may be challenging to observe at the LHC, the International Linear e+e- Collider (ILC) with s>2mHiggsino would serve as both a SUSY discovery machine and a precision microscope. We study Higgsino pair production signatures at the ILC based on a full, geant4-based simulation of the ILD detector concept. We examine several benchmark scenarios that may be challenging for discovery at the HL-LHC due to mass differences between the Higgsino states between 20 and 4 GeV. Assuming s=500 GeV and 1000 fb-1 of integrated luminosity, the individual Higgsino masses can be measured to 1%-2% precision in the case of the larger mass differences, and at the level of 5% for the smallest mass difference case. The Higgsino mass splittings are sensitive to the electroweak gaugino masses and allow extraction of gaugino masses to ∼3%-20% (depending on the model). Extrapolation of gaugino masses via renormalization group running can test the hypothesis of gaugino mass unification. We also examine a case with natural generalized mirage mediation, where the unification of gaugino masses at an intermediate scale apparently gives rise to a natural SUSY spectrum somewhat beyond the reach of HL-LHC.