  We investigate the implication of Trans-Planckian Censorship Conjecture (TCC)
for the initial state of primordial perturbations. It is possible to set the
state of perturbation modes in the infinite past as the Minkowski vacuum, only
if the pre-inflationary era is past-complete. We calculate the evolution of the
perturbation modes in such a pre-inflationary era and show that at the
beginning of inflation the perturbation modes with wavelengths much shorter
than the Hubble scale (but still larger than the Planck length scale) will
behave as they are in the Bunch-Davis state. Therefore, a past-complete
pre-inflationary evolution may automatically prepare the initial state required
for the inflationary perturbations at the CMB window while obeying the TCC.
