A fuel injection system for an internal combustion engine has a lubricity improver supply for adding a lubricity improver to low-viscosity fuel supplied to a fuel injection apparatus of the engine. The spring is configured to form a closed loop. Then, the server retrieves data of the determined music content or effect tone content from a database, and transmits the data of the visual content, along with the data of the music content or effect tone content, to the client terminal. A controller receives a signal from the mass flow meter indicative of the reverse flow.