10 000 500 000 and more preferably 50 000 250 000 as a weighted mean the reactivity with dye molecules falls if the weight average molecular weight is larger than 500 000 and the water resistance of the record image cannot be increased conversely if the weight average molecular weight is less than 10 000 the reactivity with dye molecules increases too much so when the resin comes in contact with ink it reacts rapidly with the dye molecules in the ink to produce a precipitate and in this case the ink absorptivity of the recording medium falls although the cationic resin of this invention is thought to be generated by the copolymerization of a secondary amine ammonia epihalohydrin compounds and a crosslinking agent the molecular structure of this cationic resin has not yet been elucidated by the inventor and others the state of the reaction system in the synthetic end phase of this cationic resin is solution like or colloid like and the ph is 4 9 the color is light yellow yellow yellow brown dark reddish brown or brown the additive having the cationic resin of this invention as principal component referred to hereafter simply as additive may be the solution obtained when the synthesis of the cationic resin composition of this invention is complete or alternatively it may be used in the colloid state as it is the solvent or unreacted monomer may of course also be removed moreover reagents such as a stabilizing agent.