Since 2005, OISCA is organizing tsumiki no hiroba in various parts of Japan involving primary schoolchildren. The main materials used are wooden blocks similar to the plastic LEGO toys commonly played by children. The tsumiki blocks are just like the plastic legos with shapes like cubes, rectangles and triangles. The blocks are made from Japanese cypress trees cut from thinning the forest.
OISCA as a NGO that promotes environmental conservation and protection incorporated the concept of environmental education through the tsumiki activities. Prior to the actual tsumiki events, brief lectures using visual aids and panels are shown by the tsumiki instructors to inform the participants of the source of the wood used in making the tsumiki and so as to emphasize the importance of the forest conservation and protection.
OISCA Japan including its headquarters and chapters has a total of 530,000 pieces of tsumiki blocks. Various campaigns are conducted to encourage the participation of university students, kindergarten teachers and other concern individuals to becometsumiki instructors. This is to widen and strengthen the network of tsumiki enthusiasts as well as to promote environmental conservation among the children.