For nonentangled Rouse chains, undergoing head-to-head, association and dissociation reaction, the viscoelastic relaxation functions,, MO and g(2)(t) were formulated for a Case that a given dissociated unimer chain rapidly reassociates with its original partner unimer. The relaxation of the unimer and dimer was essentially determined, by ratios r(a) and r(d) of the Rouse relaxation time (in the absence of reaction) to the association and dissociation times. For small r(a) and r(d), the reaction was slow so that the unimer and dimer relaxed through respective Pure Rouse modes, as naturally expected. however, for most cases in wide ranges of r(a) and r(d), the dimer relaxation was accelerated with increasing r(d). (>1), and g(2) of the dimer was indistinguishable from the pure Rouse relaxation function of the Unimer, g(1,Rouse). Pot those cases; g(1) of the unimer also, coincided with g(1,Rouse). These results demonstrate that the motional coupling between the unimer and diner, occurring through the association/dissociation reaction, strongly affects the relaxation: The Rouse modes of the unimer and diner were found to split in two series :clue to this coupling, and new relaxation modes due to the coupling emerged as well Those new modes largely contribute to g(1) and g(2) for the cases of r(a), r(d) > 1, thereby compensating the difference between the split modes (involved in g(j)) and the pure Rouse modes (in g(1),(Rouse)) to provide the unimer and dimer with the superficial coincidence between their g(j) and g(1,Rouse). In addition, in limited cases of moderately small rd, the relaxation of odd modes of the dimer was accelerated by the dissociation but remained still slower than the relaxation of g(1,Rouse). For this case, the unimer relaxation was slower than its pore Rouse relaxation (namely, the unimer relaxation was retarded by the reaction), because of the coupling with the,dimer odd modes. This result confirmed the significant effect of motional coupling on the relaxation of the unimer and dimer.