Concept study of Japan extremely large telescope

The status of activities on the future planning of the optical and infrared astronomy community of Japan is reported. The community established a. working group to draw a concrete plan for ground based telescopes and space missions for the next decades. Reported in this paper are the basic concept developed for extremely large telescope. Some specific areas of related research and development, for instance optical design, new materials for segmented mirrors, new approach to fabricate aspheric segmented mirror, and other engineering activities. These might turn out to be useful for promoting the project. Japan's community is open for international collaborations in these areas.