Nikawa is animal glue made from cowhide.
-How to use-
Snap nikawa in a towel or cut with cutting pliers. Put the nikawa in 200cc of water and leave it overnight, then it becomes gelatinous. Put the gelatinous nikawa in a pan (an earthenware pot or flat snow pot is preferred) and stir at about 70℃ until it completely melts.
Then, filter it with a cloth and use it for things you want to stick together.