One of the most beloved stories of Japanese history is that of The Forty-Seven Loyal Retainers in Akoh".
The story goes that in 1703 forty-seven vassals of a lord who had been forced to commit suicide by Lord Kira raided his mansion and killed him. The vassals then committed suicide as well.
This story is retold in books, movies and traditional plays (Kabuki). There is even a museum dedicated to the event at the Sengaku-ji Temple in Tokyo where the bodies of the Lord and his retainers are buried. Every year, on the anniversary, there is a parade made up of 47 people dressed in the outfits of the retainers and many many people come to see the event.
Links:http://www.jnto.go.jp/eng/location/spot/festival/gishisai.html
http://www.timeout.jp/en/tokyo/event/6536/Gishi-sai-2012
Bonus Holiday - Happy Monkey Day!