The Byakkotai (White Tiger Force) was a unit composed of fifteen-to-seventeen-year-old young samurai organized by Aizu Domain in the Battle of Aizu during the Boshin War (1868). For its wartime structure Aizu Domain formed four units: the Suzaku-tai (mature men), Seiryu-tai (middle-aged), Byakkotai (youth), and Genbu-tai (elderly). During the new government's invasion of Aizu on August 23, 1868, twenty members of the Byakkotai's Shichi Second Unit retreated to Iimori-yama (Iimoriyama). From there they saw Tsurugajo enveloped in smoke and mistakenly believed it had fallen; saying 'The lord's (Katamori's) castle has fallen. There is nothing left for us,' nineteen of them took their own lives (one survived). In fact, Tsurugajo had not yet fallen. This tragedy is deeply engraved in the Japanese heart as a symbol of the shadow side of the Meiji Restoration. The graves of the Byakkotai members on Iimori-yama are visited by many pilgrims every year, who pay their respects to the pure loyalty and tragic end of those young men. Beside the graves stands the Sazaedo of Iimori-yama (the former Entsutsu Sanso-do of Shosoji Temple), famous for its unique spiral structure.

Embodiments of pure loyalty and bushido spirit that transcended their youth. The image of those young men choosing to take their own lives without hesitation the moment they believed the castle had fallen simultaneously embodies the sublimity and sadness of bushido.

The tragedy of the Byakkotai continues to be passed down as an event that symbolizes the complexity and sorrow of Japan's Bakumatsu era and Meiji Restoration. The historic sites on Iimori-yama are representative tourist destinations of Aizu-Wakamatsu City, and many people visit every year to pay their respects to the Byakkotai.