Muramasa is an exiled swordsmith who appears in the story as a master craftsman living in seclusion. He previously forged a special sword for Yagyu Tajimanokami Munenori, a blade capable of cutting demonic spirits. After Tajima’s death and resurrection, the swordsmith is sought out by Yagyu Jubei, who learns of the sword’s purpose. Muramasa has adopted a young woman named Otsu, the niece of Miyamoto Musashi’s abandoned wife, and lives quietly with her. His personality is that of a weary but resolute artisan who understands the weight of his creations. He is initially reluctant to forge another such weapon, but after Musashi attacks his home in search of Jubei, he is convinced of the necessity. He completes a second demon-slaying sword for Jubei, declaring that it can even kill God, and then dies from exhaustion. His motivations are rooted in a sense of duty and perhaps a desire to end the chaos caused by the resurrected demons. Muramasa’s role in the story is that of a crucial ally who provides the protagonist with the only weapon capable of defeating the demonic forces. His relationship with Jubei is that of a mentor figure and supplier of the necessary tool, while his bond with Otsu shows a protective, fatherly side. He undergoes little personal development, but his sacrifice underscores the severity of the threat. His notable ability is his unparalleled swordsmithing skill, particularly the forging of blades imbued with the power to harm supernatural beings.