  We consider the Higgs portal $Z_2$ scalar model as the minimal extension of
the Standard Model (SM) to incorporate the dark matter. We find that the dark
matter mass is bounded to be lighter than 1000\,GeV within the framework that
we have proposed earlier, where the Higgs inflation occurs above the SM cutoff
$\Lambda$, thanks to the fact that the Higgs potential becomes much smaller
than its typical value in the SM: $V\ll\Lambda^4$. We can further fix the dark
matter mass to be $400\text{GeV}< m_\text{DM}<470\text{GeV}$ if we impose that
the cutoff is at the string scale $\Lambda\sim10^{17}\text{GeV}$ and that the
Higgs potential becomes flat around $\Lambda$, as is required by the multiple
point principle or by the Higgs inflation at the critical point. This
prediction is testable by the dark matter detection experiments in the near
future. In this framework, the dark matter and top quark masses are strongly
correlated, which is also testable.
