An image forming apparatus including an image forming unit, a unit holder, and circuitry is provided. The image forming unit includes a color toner unit, a replaceable black toner unit, and a replaceable special toner unit that form a color toner image, a black toner image, and a special toner image, respectively. The unit holder selectively and detachably holds the replaceable black toner unit or the replaceable special toner unit. The circuitry controls the image forming unit to perform: a normal operation, when the unit holder holds the replaceable black toner unit, that forms a color-black image; a special operation, when the unit holder holds the replaceable special toner unit, that forms a color-special image; and a toner amount increase control that increases an amount of the color toner per unit area in the color toner image in the special operation than that in the normal operation.