  A light fermionic weakly interacting massive particle (WIMP) dark matter is
investigated by studying its minimal renormalizable model, where it requires a
scalar mediator to have an interaction between the WIMP and standard model
particles. We perform a comprehensive likelihood analysis of the model
involving the latest but robust constraints and those will be obtained in the
near future. In addition, we pay particular attention to properly take the
kinematically equilibrium condition into account. It is shown that near-future
experiments and observations such as low-mass direct dark matter detections,
flavor experiments and CMB observations play important roles to test the model.
Still, a wide parameter region will remain even if no WIMP and mediator signals
are detected there. We also show that precise Higgs boson measurements at
future lepton colliders will significantly test this remaining region.
