Mosuke(喪助) was once a great blacksmith and the childhood friend of Amidamaru.
Mosuke, even though he usually acts like a calm headed adult, can, when he is with Amidamaru, become like a child again who cannot restrain his emotions, as seen when they finally met as spirits in volume 3 of the manga series, where He punches Asakura Yoh right in the face.
In his childhood Mosuke lived alongside Amidamaru and several other orphans in the feudal Japan. He had been taught by his father how to forge steel and metal. He made the sword Harusame ("Sword of Light" in the English Anime) out of his father's knife.
After Amidamaru revealed why he could not leave to Yoh and Manta, Yoh dragged Manta to museum in order to see the sword. It was then Mosuke made his first official appearance. His spirit was resting upon the broken blade and had been doing so for over 600 years. There he told his and Amidamaru' story to Yoh and Manta and revealed that he was unable to pass on until he gave Harusame back to Amidamaru. After Yoh revealed that Amidamaru was still waiting for him, he used Hyoi Gattai with Mosuke and brought the Harusame to the nearest blacksmith for repair. Later, after bringing Harusame to Amidamaru, Yoh revealed that Mosuke could not bring himself to see him and had already passed on.
When Amidamaru saved Umemiya Ryunosuke from being possesed by Tokagero he was forced to break Harusame. To repay his debt Ryu allowed for Kyōyama Anna to summon Mosuke and place him inside his body, while Amidamaru was within Yoh's body. At first both spirits punched each other for the 600 years waiting and Amidamaru breaking another of Mosuke's swords. But they were also happy to finally see each other and eventually Harusame was repaired.
In the manga Mosuke goes to the otherworld after meeting with Amidamaru in volume 3. He is later summoned back when the Archangel Michael breaks Harusame so that he can repair it. However, in the anime he appears again when some spirit sealers want to seal Amidamaru and then uses a controlled Mosuke to possess Oyamada Manta and attack Yoh and the others. However Manta figures how to create an oversoul and uses his laptop in combination with Mosuke to create a large hammer. Later on it is revealed that Mosuke has become trapped inside the laptop.
- Shaman King Manga - Chapter 2
- Shaman King Manga - Chapter 25, Pages 18-21
- BlackSmith - A Wikipedia Article about the profession of Mosuke.