Abstract: A wet-responsive fiber having a monofilament formed from a resin composition comprising a resin having an anionic group, a resin having a cationic group, and, optionally, a resin as a base. The fiber can be produced by melting and kneading a resin composition comprising a resin having an anionic group, a resin having a cationic group and, optionally, a base resin, and then conducting spinning. The nonwoven fabric is comprised of fibers of a resin composition comprising a cationic resin, an anionic resin and, optionally, a regenerated cellulose which can be used as a body fluid absorber or a wet tissue. The nonwoven fabric has water decomposability and is disposable.