The reception of Popper in Japan has not been a glorious history up to the present day. There have been numerous misunderstandings and distortions. It is important to record and discuss them in order to learn from them and to make use of his ideas in the Japanese intellectual climate. This is the purpose of the present paper. From the perspective of the reception history, we searched the reasons why Popper has been misunderstood in Japan (especially in four areas: philosophy, economics, history, and political philosophy), and tried to identify some of the factors responsible for this misunderstanding. To this end, we applied the method of “situational analysis” to the Japanese peculiar intellectual situation after the so-called après guerres, rather than by using a chronological order. If the causes of misunderstandings and distortions in Japan can be clarified by means of a situational analysis, we can learn a great deal from this history and can use this knowledge to throw new light on the status of critical rationalism in Japan