  Techni-dilaton (TD) was proposed long ago in the technicolor (TC) near
criticality/conformality. To reveal the critical behavior of TD, we explicitly
compute the nonperturbative contributions to the scale anomaly
$<\theta^\mu_\mu>$ and to the techni-gluon condensate $<G_{\mu\nu}^2>$, which
are generated by the dynamical mass m of the techni-fermions. Our computation
is based on the (improved) ladder Schwinger-Dyson equation, with the gauge
coupling $\alpha$ replaced by the two-loop running one $\alpha(\mu)$ having the
Caswell-Banks-Zaks IR fixed point $\alpha_*$: $\alpha(\mu) \simeq \alpha =
\alpha_*$ for the IR region $m < \mu < \Lambda_{TC}$, where $\Lambda_{TC}$ is
the intrinsic scale (analogue of $\Lambda_{QCD}$ of QCD) relevant to the
perturbative scale anomaly. We find that $-<\theta^\mu_\mu>/m^4\to const \ne 0$
and $<G_{\mu\nu}^2>/m^4\to (\alpha/\alpha_{cr}-1)^{-3/2}\to\infty$ in the
criticality limit $m/\Lambda_{TC}\sim\exp(-\pi/(\alpha/\alpha_{cr}-1)^{1/2})\to
0$ ($\alpha=\alpha_* \to \alpha_{cr}$) ("conformal edge"). Our result precisely
reproduces the formal identity $<\theta^\mu_\mu>=(\beta(\alpha)/4 \alpha)
<G_{\mu\nu}^2>$, where $\beta(\alpha)=-(2\alpha_{cr}/\pi)
(\alpha/\alpha_{cr}-1)^{3/2}$ is the nonperturbative beta function
corresponding to the above essential singularity scaling of $m/\Lambda_{TC}$.
Accordingly, the PCDC implies $(M_{TD}/m)^2 (F_{TD}/m)^2=-4<\theta_\mu^\mu>/m^4
\to const \ne 0$ at criticality limit, where $M_{TD}$ is the mass of TD and
$F_{TD}$ the decay constant of TD. We thus conclude that at criticality limit
the TD could become a "true (massless) Nambu-Goldstone boson" $M_{TD}/m\to 0$,
only when $m/F_{TD}\to 0$, namely getting decoupled, as was the case of
"holographic TD" of Haba-Matsuzaki-Yamawaki. The decoupled TD can be a
candidate of dark matter.
