Tenugui (Firefly)Description The larger ones are called 'Genji fireflies' and the smaller ones 'Heike fireflies.' This naming is inspired by the summer nights when fireflies dance in swarms, reminiscent of historical battles. In ancient times in Japan, it was believed that the spirits of the deceased transformed into fireflies. By simply inserting this rod into the top and bottom of a tenugui, you can easily create a tapestry.