Kage no Densetsu (影の伝説) is a story based in old Japan. The beautiful princess Kiri has been kidnapped by evil ninjas. Many samurai warriors were sent to rescue her. None ever returned. The player is Kage, a young ninja who goes to rescue the princess Kiri.
Speedrunwise, this game is all about Luckmanipulation. Like any good ninja game, it hides many secrets inside, and the player (Bisqwit) set out to discover every one of them that is important in making a TAS. A detailed story of those secrets can be found in the submission message, but in conclusion it lead into this 28-second speedup compared to the previous movie by Walker_Boh.
The theme music of this game sounds a lot better if you imagine it being played on a Japanese koto, like this: http://bisqwit.iki.fi/music/misc/kage.mid