  We investigate chiral and conformal properties of the lattice QCD with eight
flavors (Nf=8) through meson spectrum using the Highly Improved Staggered Quark
(HISQ) action. We also compare our results with those of Nf=12 and Nf=4 which
we study on the same systematics. We find that the decay constant F_pi of the
pseudoscalar meson "pion" is non-zero, with its mass M_pi consistent with zero,
both in the chiral limit extrapolation of the chiral perturbation theory
(ChPT). We also measure other quantities which we find are in accord with the
pi data results: The rho meson mass is consistent with non-zero in the chiral
limit, and so is the chiral condensate, with its value neatly coinciding with
that from the Gell-Mann-Oakes-Renner relation in the chiral limit. Thus our
data for the Nf=8 QCD are consistent with the spontaneously broken chiral
symmetry. Remarkably enough, while the Nf=8 data near the chiral limit are well
described by the ChPT, those for the relatively large fermion bare mass m_f
away from the chiral limit actually exhibit a finite-size hyperscaling
relation, suggesting a large anomalous dimension gamma_m ~ 1. This implies that
there exists a remnant of the infrared conformality, and suggests that a
typical technicolor ("one-family model") as modeled by the Nf=8 QCD can be a
walking technicolor theory having an approximate scale invariance with large
anomalous dimension gamma_m ~ 1.
