White Oak leaf motif.  The oak leaf in ancient times was used to serve food on.  Eventually they became iconic of offerings to the gods and became a revered symbol too the followers of Shinto.
 

In this set the tsuba is a lenticular shaped iron plate. The three leafs decorating the front and back are carved in shishiaibori technique. This is where the carving is done in the base metal so the carving is below the original surface. What distinguishes it is that the surrounding ground is not lowered around the carving which technically would make it a raised carving. With shishiaibori the designs give a raised appearance even though they are sunken. Its one of my favorite techniques

The gold accents symbolize "rot". They are applied with a technique called Nunome Zogan. In this technique a fine pattern of teeth are raised on the iron surface. The gold is layed down on these teeth and hammered in place. It is a touchy process, but if done correctly it is very durable. The gold is much thicker than gold leaf or typical electroplating. It stands proud of the surface.

The remaining pieces (Fuchi, kashira, Menuki, Kurigata, and Kojiri) are made from Shakudo which is a copper and gold alloy . The ingot that all these parts were formed from also contains small amount of silver and traces of many other elements which enhance the color. All of these pieces were seamlessly raised from sheet.

The gold accents on the shakudo are typically done with solid inlay or Kinkeshi which is a process involving mercury. Its rather toxic and illegal to use without special ( read expensive) equipment to recover the mercury vapors. So this gold was applied with an electroplateing process. The thickness of the gold is built up over time. Many times thicker than any electroplateing you find on jewelery. This is necasary to stand up to the rigors patina preparations. Standard plateing is so thin it would literally be wiped away by the abrasive preparations that are required for shakudo to color properly.