''Nazo no Murasamejō'' (in English, ''The Mysterious Murasame Castle'') is a medieval Japanese fantasy video game created by Nintendo and released in 1986 as the second original title for the FamicomDiskSystem, after ''VideoGame/TheLegendOfZelda'', to which it has some resemblance. The game has been occasionally rereleased, eventually coming to Europe and America as well courtesy of the 3DS Virtual Console.

The game takes place during the Edo period, where Murasame and four neighboring castles have been possessed by a demonic force. It falls to a young swordsman named Takamaru to defeat Murasame.

Despite having only one game in the series (and one that until recently was not released outside of Japan), this game had had a rather interesting legacy. Takamaru featured in the Wii version of ''[[VideoGame/SamuraiWarriors Samurai Warriors III]]'', which also included a full remake of his game. Takamaru also appeared in ''VideoGame/CaptainRainbow'' as one of the inhabitants of the island, and ''VideoGame/NintendoLand'' has an attraction based off of ''The Mysterious Murasame Castle''. Finally, Takamaru appeared in ''[[VideoGame/SuperSmashBros Super Smash Bros. Brawl]]'' as a Sticker, and he will appear in the fourth game as an Assist Trophy.
* BulletHell: With enemies everywhere throwing projectiles left, right, up, and down, the game will sure feel like one.
* ColourfulThemeNaming: The four castles besides Murasame, Aosame, Akasame, Ryokusame and Momosame, are named after Japanese colors.
* ContinuingIsPainful: Most powerups are lost upon death.
* FlipScreenScrolling: Throughout the game.
* IaijutsuPractitioner: Takamaru uses his sword by unsheathing and re-sheathing it. His pose when not moving even shows him grasping his sword ready to strike.
* ImpossiblyCoolWeapon: Getting enough shuriken upgrades results in shuriken with explosive lightning.
* NintendoHard: As with all games of [[The8BitEra the era]].
* OneManArmy: Takamaru fights ''hundreds'' of enemies throughout the game. It helps that enemies respawn endlessly.
* TimedMission: Every level has a time limit, although the timer resets every time Takamaru loses a life.
* TheVeryDefinitelyFinalDungeon: The titular Murasame Castle, where the floor is black and the walls are NothingButSkulls.