Aqueous pigment ink composition for inkjet printing, image forming method, formed image, ink set and inkjet printer

An aqueous pigment ink composition for inkjet printing, which contains a pigment, a dispersant, an emulsion resin, water and an aqueous organic solvent, and which is characterized in that: the emulsion resin has an average particle diameter of 70 nm or less, said average particle diameter being less than the average particle diameter of the pigment; the content of the emulsion resin is equal to or more than the content of the pigment and is from 2% by mass to 10% by mass (inclusive) relative to the total mass of the aqueous pigment ink composition for inkjet printing; and the aqueous organic solvent contains 3-methoxy-3-methylbutanol and a pyrrolidone-based solvent respectively in amounts within the range of from 2% by mass to 18% by mass (inclusive) relative to the total mass of the aqueous pigment ink composition for inkjet printing.