Muramasa: The Demon Blade is a 2009 action role-playing game developed by Vanillaware and published for the Wii by Marvelous Entertainment (Japan), Ignition Entertainment (North America), and Rising Star Games (Europe). Set in the Edo period during the reign of shogun Tokugawa Tsunayoshi, conflicts have arisen over ownership of the Demon Blades, samurai swords forged by Muramasa Sengo that bring tragedy and madness upon their wielders. The story follows two protagonists related to this conflict: Momohime, a woman who is possessed by the spirit of vengeful rōnin Jinkuro Izuna; and Kisuke, an amnesiac ninja on the run for a forgotten crime who is tied up with the tragedy that destroyed Momohime's family. Using a 2D side-scrolling perspective, the gameplay revolves around a beat 'em up fighting system, while incorporating role-playing elements such as leveling and questing.

The concept work for Muramasa began during the middle of development on Odin Sphere. Along with improving on the action gameplay over Odin Sphere, a great deal of effort was put into making the game's setting authentic to the period. Director and writer George Kamitani created the story based on kabuki theatre, incorporating Japanese folklore and Buddhist theology. When the game was released in the West, it retained its Japanese voicetrack to preserve its atmosphere. It was released to moderate sales and positive reviews. Praise focused on its art design and music, with the gameplay often described as fun but shallow, and its story was faulted for its structure

A PlayStation Vita version, titled Muramasa Rebirth in the West, was published in 2013 by Marvelous AQL in Japan and Aksys Games in English territories. Rebirth was supported by downloadable content in the form of Genroku Legends, four self-contained stories based on Japanese folklore. The game featured new music, and a redone localization. Rebirth met with strong sales, and a similar reception to its original version. Another version, Muramasa: Revenant Blades, is set for release worldwide in 2027 for PlayStation 5, Nintendo Switch, Nintendo Switch 2 and Windows. Published by Marvelous, it includes all the content of Muramasa Rebirth, upgraded graphics and added gameplay options, and another new localization with an English dub.

Muramasa is a two-dimensional (2D) side-scrolling action role-playing game set on the main Japanese island of Honshu during the Edo period. Players take control of two characters with similar gameplay abilities. Navigation takes place through hand-drawn 2D side-scrolling environments reminiscent of Japanese artwork of the period, and can enter towns to talk with non-playable characters (NPCs) and buy items such as health restoratives and accept quests. An additional cooking element allows the characters to cook meals using materials gathered during exploration: meals grant temporary character boosts, and fill a "fullness" meter that limits how much food a character can eat.

Combat comes in the form of both avoidable random encounters and scripted fights where the camera is fixed within the fighting area: enemies and bosses are primarily drawn from Japanese folklore and mythology. Battles are triggered only when enemies are near, with the player character otherwise keeping their weapons sheathed. In combat, characters attack and guard using a single-button prompt, while another button accesses items such as healing potions. Continuously attacking triggers combos. Different moves include sword slashes combined with directional buttons, which have different effects such as throwing an enemy into the air with an upward slash. Additional offensive items such as smoke bombs are acquired during the course of the game. At the end of each battle, experience points are awarded to the player character depending on how fast the battle was finished: leveling up increases a character's health, stats, and the amount of damage inflicted upon enemies.

Weapons are distinguished into two categories, Blade (katana) and Long Blade (nōdachi): Blades are fast, while Long Blades are slower and deal higher damage. Three blades can be equipped at any one time: each blade has its own stats, determining the amount of damage that can be inflicted. When blocking or using a blade's Secret Art special move, its Soul Power gauge depletes: if emptied, the sword breaks and its offensive abilities are drastically reduced. When sheathed, the Soul Power regenerates. Soul Power can be gathered in various locations to restore Soul Power and the character's health. There are 108 blades that can be collected and forged in-game: forging blades requires Soul Power and "spirit", and each blade has a level cap determining when it can be forged. Weapon forging is governed by a weapon-based skill tree.

Muramasa takes place on Honshu, the main island of the Japanese archipelago, with its overall style and setting drawing heavily upon Japanese folklore and mythology. It is set in the Genroku period, itself within the larger Edo period, during the reign of the shogun Tokugawa Tsunayoshi. Tsunayoshi's thirst for power has created conflict around ownership of the Demon Blades, samurai swords forged by the legendary swordsmith Muramasa Sengo that crave blood when drawn and bring madness and death to those foolish enough to draw them. Due to the chaos generated by this, the Demon Blades' powers begin summoning demons from Hell (Yomi), along with causing ancient gods to stir from long slumber.

The two lead characters are Momohime (百姫), a princess of the Narukami clan from the province of Mino; and Kisuke (鬼助), a runaway ninja with no memories but a burning desire for vengeance. For the course of the game, Momohime is inadvertently possessed by the spirit of Jinkuro Izuna (飯綱 陣九朗), an unscrupulous rōnin who was trying to possess the body of Momohime's betrothed Yukinojo Yagyu (柳生 雪之丞), a high-status samurai. Momohime and Kisuke are each accompanied and watched over by a kitsune in human form. They are Kongiku (紺菊), who holds affection for Jinkuro, and Yuzuruha (弓弦葉), who aids Kisuke in his quest against the Demon Blades' corruption. A key character in Kisuke's storyline is Torahime (虎姫), Momohime's sister.