There is provided a technique that includes: (a) performing a cycle including supplying a source containing a predetermined element, carbon, and hydrogen to a substrate and supplying a first modifying agent containing nitrogen to the substrate, a predetermined number of times to form, on the substrate, a first film containing the predetermined element, nitrogen, carbon, and hydrogen bonded to carbon; and (b) supplying, to the substrate on which the first film is formed, a second modifying agent that is different from the first modifying agent and contains a compound containing a nitrogen-hydrogen bond and a nitrogen-nitrogen bond per molecule or a derivative of the compound, to modify the first film to a second film that is lower in content rate of the hydrogen bonded to carbon than the first film and contains the predetermined element, carbon, and nitrogen.