  The supersymmetric SU(5) grand unified theory with the gauge symmetry broken
by the Hosotani mechanism naturally solves the mass hierarchy problem between
the colored Higgs triplet and the electroweak Higgs doublet, and predicts the
existence of adjoint chiral superfields with masses of the order of the
supersymmetry breaking scale as a byproduct. In addition to the two SU(2)_L
Higgs doublets of the minimal supersymmetric standard model, the Higgs sector
is extended by an SU(2)_L triplet chiral supermultiplet with hypercharge zero
and a neutral singlet one. Such new triplet and singlet chiral supermultiplets
deviate the standard model-like Higgs boson couplings and the additional Higgs
boson masses from their Standard Model predictions. We show that this model can
be distinguished from other new physics models using by precisely measuring
such Higgs couplings and masses, and that our model is a good example of grand
unification testable at the luminosity up-graded Large Hadron Collider and
future electron-positron colliders.
