External additive, method for manufacturing external additive, and toner

An external additive comprising:

• a resin particle containing a crystalline resin and an inorganic fine particle containing a metal atom, the inorganic fine particle being embedded in the resin particle with a part of the inorganic fine particle being exposed on a surface of the resin particle, wherein
• a maximum endothermic peak in differential scanning calorimetry of the external additive is from 50.0 to 120.0° C. during a first temperature rise,
• the external additive has a shape factor SF-2 of 110 to 150 as measured in a scanning electron microscope image at a magnification of 200,000, and
• Za≥15 and Za/Zb≥1.0
• where Za (mass %)={dm×(atomic weight of the metal atom)}/[{dC×(atomic weight of carbon)}+{dO×(atomic weight of oxygen)}+{dm×(atomic weight of the metal atom)}]×100,
• dm represents a concentration of the metal atom on a surface of the external additive obtained by X-ray photoelectron spectroscopy,
• represents a concentration of carbon atom at the surface of the external additive obtained by X-ray photoelectron spectroscopy,
• dO represents a concentration of oxygen atom at the surface of the external additive obtained by X-ray photoelectron spectroscopy, and
• Zb (mass %)=(mass of the metal atom obtained from an ash content derived from the inorganic fine particle, the ash content being obtained by heating the external additive at 900° C. for 1 hour)/(mass of the external additive)×100.