  We construct a model realizing the inverse seesaw mechanism. The model has
two types of gauge singlet fermions in addition to right-handed neutrinos. A
required Majorana mass scale (keV scale) for generating the light active
neutrino mass in the conventional inverse seesaw can be naturally explained by
a "seesaw" mechanism between the two singlet fermions in our model. We find
that our model can decrease the magnitude of hierarchy among the mass
parameters by $\mathcal{O}(10^4)$ from that in the conventional inverse seesaw
model. We also show that a successful resonant leptogenesis occurs for
generating the baryon asymmetry of the universe in our model. The desired mass
degeneracy for the resonant leptogenesis can also be achieved by the "seesaw"
between the two singlet fermions.
