''Nazo no Murasame Jō'' (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 {{UsefulNotes/Famicom}}, after ''VideoGame/TheLegendOfZeldaI'', 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. Fuji TV developed a live-action TV drama loosely based on the game with Sanae Jonouchi starring as Kayo and the Snow Princess and Masaki Kyomoto as Seikichi and the White Rabbit/Takamaru. Later, Takamaru was 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 appeared in the fourth game as an Assist Trophy, and music from ''Nazo no Murasamejō'' featured in both games. There's also a Mii costume based on him.
!!This game provides examples of:
* ActionBomb: Flashing ninjas explode when killed, requiring the player to kill them at a distance.
* BulletHell: With enemies everywhere throwing projectiles left, right, up, and down, the game will sure feel like one.
* ChestMonster: Some princesses in the castles aren't actually princesses at all, but are [[ImplacableMan resilient]] evil spirits that will slowly give chase until you defeat them.
* ColourfulThemeNaming: The first four castles, Aosame, Akasame, Ryokusame and Momosame, are named after Japanese colors and are appropriately ColorCodedForYourConvenience.
* CounterAttack: You can deflect shuriken with you sword by attacking when said projectiles are within sword range. You can't deflect bombs, fireballs or gusts of wind, though.
* ContinuingIsPainful: Most powerups are lost upon death.
* DeathOrGloryAttack: You can fell most enemies faster with your sword than you can with just projectiles. Getting in range is another matter.
* FlipScreenScrolling: Throughout the game.
* HighlyVisibleNinja: The most common enemy faced 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 most games of [[UsefulNotes/The8bitEraOfConsoleVideoGames the era]].
* OneManArmy: Takamaru fights ''hundreds'' of enemies throughout the game. It helps that enemies respawn endlessly.
* PublicDomainSoundtrack: The ending features a rendition of the "Ode to Joy" from Ludwig van Beethoven's Symphony No. 9.
* SmartBomb: The Inazuma Lightning, which clears all enemies on the screen and even reveals hidden Tanuki.
* {{Tanuki}}: They serve as suppliers of your armament.
* TechnicolorNinja: Alongside the standard black, ninjas in this game come in white, red, blue, green, flashing… overlaps with HighlyVisibleNinja.
* {{Tengu}}: Who will impede your progress with a combination of TeleportSpam and [[RazorWind gusts of wind]]
* 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.