  We propose a neutrino mass matrix model in which five neutrino species remain
light through the seesaw mechanism within a supersymmetric $3\nu_L+3\nu_R$
framework. We construct such a model based on the nonrenormalizable terms in
the superpotential constrained by the discrete symmetry which may be expected
in the models at the high energy scale such as superstring. We study the
possible oscillation phenomena by fixing mass parameters so as to explain the
solar and atmospheric neutrino deficits and also include a candidate of the
suitable dark matter. We also discuss the charged lepton mass matrix based on
this neutrino model. LSND results may be consistently explained within this
model.
