  We present the analytic forms for the spectra of the cosmological
perturbations from an initially anisotropic universe for the high momentum
modes in the context of WKB approximations, as the continuation of the work
[29]. We consider the Einstein gravity coupled to a light scalar field. We then
assume that the scalar field has the zero velocity initially and then slowly
rolls down on the potential toward the origin. In the slow-roll approximations,
the Kasner-de Sitter universe with a planar symmetry is a good approximation as
the background evolution. Quantization of the perturbations in the adiabatic
vacuum, which we call the anisotropic vacuum, is carried out. For non-planar
high momentum modes whose comoving momentum component orthogonal to the plane
is bigger than the Hubble parameter at the inflationary phase, the WKB
approximation is valid for the whole stage of the isotropization. On the other
hand, the planar modes whose comoving momentum component orthogonal to the
plane is comparable to the Hubble parameter, is amplified during the process of
the anisotropic expansion. In the final gravitational wave spectra, we find
that there is an asymmetry between the two polarizations of the gravitational
wave because the initial mode mixing does not vanish.
