  We propose an inverse seesaw model with large $SU(2)_L$ multiplet fields
which realizes natural mass hierarchies among neutral fermions. Here, lighter
neutral fermion mass matrices are induced via two suppression mechanisms; one
is small vacuum expectation value of $SU(2)_L$ triplet required by rho
parameter constraint and the other is generation of Majorana mass term of extra
singlet fermions at one-loop level. To realize the loop masses, we impose $Z_2$
symmetry which also guarantees stability of a dark matter candidate.
Furthermore, we discuss anomalous magnetic moment and collider physics from
interactions of large multiplet fields.
