This study examined the development of the metaphorical and metonymic meanings of the words black and white appearing in Japanese contexts by contrasting the meanings in Japanese with the original meanings in English. It investigated the semantic shifts which affected grammatical structures in highly real-time language on Twitter. The study revealed that black and white in Japanese contexts were used metaphorically in the narrow sense of the original English meaning. Black was used in the meanings of break the rules, persecute, and take advantage while white was used in the opposite manner. Nevertheless, these meanings do not appear in English contexts. It is a semantic change for specific usages in Japanese contexts. At first, the words black and white were mainly used with the noun company as compounds. Then, their meanings were expanded in a metonymic manner with the contiguity of senses. In other words, from being used to describe a characteristic of a company, black and white are later used to describe the characteristic of a company worker and an action of a person. The usage also changes from a compound noun to a single word in a predicate and as an adjective na.