My encounter with chitosan, which is said to be an ecosystem preserving agent, has connected me to the worlds of health, agriculture, the environment, and food. It has been discovered that crab shells, which were originally disposed of as industrial waste, play an important role in the ecosystem. Chitin and chitosan, which are also present in the cell walls of microorganisms, have a common molecular structure (pathogen-associated molecular pattern: PAMP) that microorganisms have, and are recognized by humans, plants, and mammals through pattern recognition receptors (PRR) , so they can be used not only as health foods, but also in the fields of agriculture and livestock farming. There are probably still many things that exist in nature whose meanings have not been clarified, but fortunately, chitin and chitosan have been elucidated, and it has been revealed that they are extremely safe and have no environmental impact. These facts are thanks to the efforts of many researchers and related parties who have been involved in chitosan research. We believe that our mission is to convey the function and usage of the unique substance called chitosan, and we work every day with this in mind.