An on-chip multicomponent system is implemented on a III-nitride-on-silicon platform by integrating a transmitter, InGaN waveguide, InGaN directional coupler, and receivers onto a single chip. The transmitter and the receiver share an identical InGaN/GaN multiple-quantum-well (MQW) diode structure and are produced by using the same wafer-level process flow. The receiver sensitively responds to the short-wavelength half of the emission spectrum of the transmitter, thus realizing the multicomponent system with the capability for inplane light communication. A SiO2 isolation layer is employed to decrease the p-n junction capacitance, thus improving the modulation rate without modifying the MQW structure. The wire-bonded monolithic multicomponent system experimentally demonstrates inplane data transmission at 80 Mbps and spatial light communication at 100 Mbps, paving the way for diverse applications from on-chip power monitoring to inplane light communication in the visible light spectrum.