Three years after Ieyasu Tokugawa won the Battle of Sekigahara in September 1600, he celebrated New Year's Day of 1603 in Fushimi, Kyoto. Then on February 12th, he was proclaimed Seiin Taishogun by the Imperial Court and went to the Kanto region to enjoy hawk hunting.

　The majority of the hunting grounds were in an area of wilderness in Musashino, which was 20 km west of Edo, and when traveling to that area from Sunpu, he would pass through what is called Doshi village today on his way to the hunting grounds.

　On the way there, he stopped for lunch on a riverbank that was north of Lake Yamanaka, and this was a waterless river that did not have any running water.

　As it was the beginning of the summer season, it was a hot day and the Ieyasu party sent one of the attendants to a house in the vicinity to ask for water from the well.

At that time, he was told to ask why the river did not have any water.

　After having the water in the bucket tested by an attendant to make sure it was not poisoned, Ieyasu drank the water too, and, impressed by how cool and delicious the water tasted, tried to find out why the water was not flowing in that area.

　Upon this, the attendant said that previously the water had been very deep, but as there had been multiple eruptions by Mt. Fuji, there had been a large number of deposits that had formed a riverbed. The riverbed had become like a tough mesh and the water had sunk into the waterbed and flowed down the original valley floor. Unless there was a large amount of rain, water would not flow on the surface.

When Ieyasu muttered that the cool and delicious well water from this region was “a gift from the sacred Mt. Fuji”, his attendants also tried the water, and proclaimed that they had never tasted such delicious water before.

　Following that, when Ieyasu went from Sunpu to go hawking, he frequently travelled on the road from Tokaido to Doshi Village and enjoyed drinking the famous water. He also took large quantities of this water with him on his hawking trips. The fact that he got a lot of exercise from hawking was probably a blessing as well. Ieyasu had previously complained of frequent dizziness and headaches, and this probably due to high blood pressure as a result of being overweight. However, from that time, he became moderately thin and the picture of health.

　The village here had previously had nothing to be proud of and so the people of this area who had provided Ieyasu with well water were very grateful to hear how Ieyasu had praised the well water there for improving his health. They were so grateful that they named the groundwater in this area the “Water of Sir Ieyasu" and cherished it.