This chapter aims to explain the science of Kakishibu in a way that is easy to understand even for those who have never encountered the word Kakishibu before. Beginning with an explanation of polyphenols related to the taste of green tea, it first describes the difference between these polyphenols and the astringent component of persimmons, condensed tannin, and then traditional uses of Kakishibu made from astringent persimmons which included some of tools used in traditional tea production and others, its physical and chemical properties of traditional Kakishibu, the various measurement methods of the characteristics, and how it differs from plastics made from coal and oil. It also covers its component analysis and the structure of its main polyphenolic component, kakitannin, and the entity is a huge size of proanthocyanidin polymer. It is believed that their knowledge and techniques will encourage many people to consider the new industrial possibilities and attractions of this natural high molecular substance, kakitannin. Perhaps it will provide us with clues to saving our beloved planet. The following sections are consisted in this chapter: a detailed explanation of the science behind Kakishibu. After a brief introduction to the science of Kakishibu (Sect. 4.1), the scientific explanation will progress from the macro to the micro level. It will delve from the substance of Kakishibu and products utilizing Kakishibu (Sect. 4.2) to the components contained within Kakishibu (Sect. 4.3) and finally to the molecular structure of Kakishibu’s main component, kakitannin (Sect. 4.4).