Umewakamaru was an ill-fated boy who was taken by a slave trafficker named Tōta from the ancient imperial city of Kyoto to Sumida River and then died a cruel death on the shores of Sumida River at the age of seven. The sad story of "Sumida River" features in Noh songs and Jōruri plays and the story was well known by the people of Edo. The Umewaka grave is in the grounds of Mokubo-ji Temple and the Umewaka Memorial has been conducted every year on March 15 (it is now held on April 15.)