The source of the stickiness was originally contained in the starch in potatoes and rice. When rice is boiled, it becomes sticky, which is evidence that the source of the stickiness is contained in the rice. This sticky substance becomes sticky when the rice is heated with water. Yamato Nori" is a glue made from this sticky substance in rice and potatoes.
There are various opinions about the function of this glue in sticking things together. For example, some believe that glue gets into the fibers of paper and clumps together, while others believe that glue gets stuck between sheets of paper, creating no space between them, and then the force of the atmosphere around it causes them to stick together.
This is different when it comes to glue or cemedine. For example, when plastic is bonded together, the adhesive melts the surface of the plastic, and the melted surface and the adhesive combine and stick to each other.