Hotarumaru  Hotarumaru(ほたるまる), written as 蛍丸, is a Ōdachi created by Rai Kunitoshi, swordsmith in Japan. Hotarumaru means firefly, which named by the legend which says the Ōdachi's flaw was fixed by fireflies. The Ōdachi was also called as Aso no Hotarumaru since it was stored in Aso Shrine. The Ōdachi became National Treasure in Japan at December 14, 1931. However, after World War II, it was lost.