Orientation relaxation of polymer chains with low molecular weight is known to be retarded by surrounding chains with high molecular weight. This phenomenon, i.e., intermolecular orientation correlation, has been well understood by the reptation concept and called “nematic interaction”. In this presentation, it is demonstrated that the nematic interaction occurs in a miscible blend system. The orientation of low-mass compounds having high intrinsic birefringence enhances the optical anisotropy after stretching, albeit low-mass compounds hardly affect the elongational stress. For example, poly(lactic acid) with low molecular weight shows strong orientation in a molten cellulose ester having high viscosity during stretching. Furthermore, even plasticizer molecules are oriented to the stretching direction via orientational couplings with the molecules of cellulose esters. As a result, the stretched blends exhibit strong orientation birefringence, which can be used to modify the birefringence and its wavelength dispersion for a retardation film.