  Effects of matrix orientifolding that preserves supersymmetries are
considered in the IIB matrix model with regard to its effective dynamics
generated for diagonal elements. Taking the case of maximal supersymmetries and
the long distance expansion of the one-loop effective action as well as cases
where the size of the matrices is small, we demonstrate that the directional
asymmetry of spacetime brought upon by this setup in fact leads to that of the
forces exerting on the spacetime points: in addition to the two-body attraction
between two points, there are attractions toward the four dimensional plate.
