Apparently the story goes that these 19 samurai were returning from battle they looked out over their city and it was on fire. Feeling like this was a sign of their failure they decided that rather than return to the city as failures it was more honorable to take their own lives. The tragedy is that the city itself was not conquered it was merely a unrelated fire so their deaths were an unfortunate misunderstanding, but because of their honorable sacrifice the shrine was errected in their memory.