Inverse seesaw model with large SU(2)_L multiplets and natural mass hierarchy

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.