An encapsulated agent includes a central part and an outer part that covers a surface of the central part. The central part contains a viscosity-reducing material that reduces viscosity of a fluid to be used in a hydrofracturing technique. The outer part contains a plurality of particulate substances and a holding material that holds the plurality of particulate substances and enables gradual release of the central part in the fluid. The outer part involves distribution of the plurality of particulate substances that allows a content to have one or more local maxima in a direction away from the central part.