Byakkotai was meant to be a reserve unit, as it was composed of the young, 16- to 17-year-old sons of Aizu samurai. It was subdivided further, along the lines of rank within the domain's samurai population: two squads were from the upper (shichū) rank, two from the middle rank (yoriai), and two from the lowest (ashigaru). Twenty of the members of the 2nd shichū squad, cut off from the rest of their unit in the wake of the Battle of Tonoguchihara, retreated to Iimori Hill, which overlooked the castle town. From there, they saw what they thought was the castle on fire, and committed seppuku (with one failed attempt) in desperation, believing their lord and families dead. However these 20 Byakkotai members were mistaken in their assessment of defeat, as the castle defenses had not actually been breached; the castle town surrounding the inner citadel was aflame. As the majority of the town was between Iimori Hill and the castle, the boys saw the rising smoke and assumed that the castle itself had fallen. (Wilkipedia)
Today the cult of this young samurai is still alive, and many people, old and young, come here to pay their tribute to the memory and burn incense. I visited the site and took the photos in Summer 2011.