In A.D.768, Wakeno Kiyomaro, a Japanese bureaucrat, was attacked by his political opponent Dokyo. He injured his leg tendon, and lost the use of his legs. Suddenly, about two hundreds of wild boars appeared from out of nowhere. They picked him up and brought him to a shrine in Kyushu. He received an oracle there: “Enter the spa at the foot of a mountain in the Kiku district.” He obeyed the message, and his leg recovered very quickly. Eventually, he revenged himself on Dokyo, and played an active part in the political world.
After that, where the spa was there was named 湯川 (Yukawa). 湯 means hot water. The mountain was named 足立山 (Adachisan). 足, 立, and 山 mean leg, stand, and mountain, respectively.”
— The legend of wild boars in Kyushu http://lang-8.com/41158/journals/242603^;
Note: In Japanese folklore and iconography of woodblock prints! the wild boar is often the steed of the tengu or the Tengu King Sojobo see Onmarkproductions http://www.onmarkproductions.com/html/tengu.shtml