The effects of adding an "inversely antagonistic" salt, tetraphenylphosphonium chloride (PPh4Cl), to a binary mixture of deuterated water and 3-methylpyridine were investigated by visual inspection and small-angle neutron scattering. With increasing salt concentration, the two-phase region shrinks and a charge density wave structure is induced, as in the case of adding a "normally antagonistic" salt, sodium tetraphenylborate (NaBPh4), to the binary mixture. The concentration range of the periodic structure is narrower than that in the case of adding NaBPh4, and no ordered lamellar structure is observed in the present study.