Current research at home and abroad has reported that the main problems in junior high school mathematics are that students have little interest in mathematics and lack their ability of logical reason and explanation. In order to solve these problems, I developed a card-based learning tool “Etomi” and practiced using this teaching material with my collaborators at several junior high schools. I believe that this material will help students to choose the best solution from several existing procedures and to explain with counterexamples what are not always true, and it will help them to use mathematical expressions such as equations,words,tables and diagrams appropriately. This paper has described the progress of the development of the teaching materials, student's interest in the teaching materials and their mathematical effects based on the results of surveys and questionnaires in the classroom. In the future I will conduct research on how to disseminate the material and how to investigate the above effects.