Resin particles each include a crystalline polyester resin, an amorphous polyester resin, a release agent, and a colorant. The crystalline polyester resin includes an acid component and an alcohol component as constitutional units, and the acid component of the crystalline polyester resin includes plant-derived dicarboxylic acid having 12 or less carbon atoms. The crystalline polyester resin is present as domains in a matrix of the amorphous polyester resin within each resin particle, an average major axis of the domains of the crystalline polyester resin is 2.0 micrometers or less, and an average aspect ratio (major axis/minor axis) of the domains is 4.0 or greater. The resin particles have a carbon radioisotope 14C concentration of 5.4 pMC or greater.