contained in an amount above 60 by weight the electron receptive compound may deposit and thereby granulation of the wax would become difficult the decolorization agent inhibits the color developing function of the electron receptive compound therefore the decolorization agent performs a function to remove or dilute a developed color given by the electron donative color developing organic compound when an erasing operation is carried out the decolorization agent is preferably a basic compound it is considered that the discoloring ability of the ink composition depends on the strength of the basicity of the decolorization agent as the basicity of the decolorization agent is stronger the color of the electron donative color developing organic compound in its colored state can be made decolorized state more successfully improving the discolorability of the ink composition by heating in the present invention as the decolorization agent it is preferable to use a compound selected from the group consisting of the following compounds an aromatic compound having at least one amino group and an alkylene group between the amino group and an aromatic ring in the molecule a compound represented by a general formula nh 2 u2014 c 2 h 4 u2014 nh u2014 c 2 h 4 n u2014 nh 2 n u2267 0 and derivatives thereof a compound generally referred to as a hindered amine which compound has a piperidyl group and derivatives thereof in the molecule the aliphatic amine is a primary amine a secondary amine or a tertiary amine the aliphatic amine is preferably the secondary amine or the tertiary amine the.