We report the observation of a remarkably strong coupling between light and a multinode-type exciton. The observed radiative decay time reaches the order of 100 fs, which is much faster than the dephasing process of nonradiative scattering. In this high-speed superradiance, the light wave and the excitonic wave in a high-quality thin film form a harmonized wave-wave coupling over a range of multiple wavelengths. This mechanism contradicts the conventional physical description of light-matter interaction based on the long-wavelength approximation.