Oligophenylenevinylene (OPV)-based fluorescent (FL) chemosensors exhibiting linear FL responses toward polyanions were designed. Their application to FL sensing of glycosaminoglycans (heparin: HEP, chondroitin 4-sulfate: ChS, and hyaluronic acid: HA) revealed that the charge density encoded as the unit structure directs the mode of OPV self-assembly: H-type aggregate for HEP with 16-times FL increase and J-type aggregate for HA with 93-times FL increase, thus unexpectedly achieving the preferential selectivity for HA in contrast to the conventional HEP selective systems. We have found that the integral magnitude of three factors consisting of binding mechanism, self-assembly, and FL response can amplify the structural information on the target input into the characteristic FL output. This emergent property has been used for a novel molecular recognition system that realizes unconventional FL sensing of HA, potentially applicable to the clinical diagnosis of cancer-related diseases.