We offer a possible explanation for the appearance of light composite fermions and Higgs bosons on a four-dimensional domain wall. The pattern of light particle trapping is attributed to a strong self-interaction of five-dimensional pre-quarks. We calculate the low-energy effective action which manifests the invariance under the so-called τ-symmetry. After that, we find a set of vacuum solutions that break the symmetry and the five-dimensional translational invariance. The induced relations between low-energy couplings for Yukawa and scalar field interactions allow us to make certain predictions for light particle masses and couplings themselves, which may provide a signature of the higher-dimensional origin of particle physics in the forthcoming experiments. Bibliography: 53 titles.