Musashi is a skilled fighting dog in Shikoku and an Ōu soldier.
Musashi is a brown (also described with reddish brown fur) Tosa dog. There's darker fur around his eyes and mouth.
Later in Ginga Densetsu Weed, he loses his left eye.
Musashi is a calm and patient dog with sense of justice, soon befriending the Ōu dogs. He is a very skilled fighter. He is polite but ready to show to the overly confident dogs their place. He also saves Akatora from Bill's dog and is ready to protect Gin with his life, showing his rightfulness and courage. He has negative opinion of Bill, seeing him as a criminal. However, he respects the Ōu dogs due to their honorable goal. Musashi rarely looses his temper and sometimes speaks sense to the other dogs. Due to his high rank as a fighting dog, he has a lot comrades in fighting dogs who listen to him. He is a true gentleman towards females. In the manga, Cross is a bit charmed by him and sees him as a handsome male. Still, she is in love with Ben and this doesn't lead to anything. Musashi shows great respect towards Benizakura.
In Ginga Densetsu Weed, Musashi keeps his calm nature and his sense of justice. He doesn't see losing in battle as humiliating but he feels deep shame when the successor he chose became a bad guy.
Musashi was a great fighting dog who had won the championship of Japan three times. He saved Akatora from the mountain dogs in Shikoku and helped Gin and the platoon when they run into an ambush made by Sniper. Musashi joins the platoon because he thought that he is getting too old to participate in fights over the championship and he would rather help the wild dogs in the fight against Akakabuto. Musashi survives the final battle against Akakabuto.
He is seen with Bemu when the other dog is killed by mysterious wolves. These wolves turn out to be Gaia's soldiers. Musashi goes to Hokkaido to fight them along with other soldiers and even wants to challenge Gaia himself at one point. He survives the battle and returns home.
After aiding Gin in the last battle against the bear Akakabuto, he returned to the fighting arena in Shikoku. When he started to lose the hang of it, he decided to end his career by losing to younger Tōbē. Later, when Musashi has ran to Ōu to help Weed, he meets Tōbē once more. He was very disappointed to see that the dog he chose as his follower had decided to join the evil Hōgen. However, Tōbē makes it up to Musashi by joining Weed and sacrifice his life to save the puppy Takeshi.
During the Russian army dog arc Musashi joined in the fight against the invading army. He loses his left eye during the fight against Bozlev's soldiers. He was seen taken to the vet along with Jaguar and Tābō by Daisuke and Hidetoshi who came to aid the wounded dogs. A few days later, when they got better (in GDW manga volume 52); he, Jaguar and Tābō had been let out by Daisuke and Hidetoshi back to the wild.
When the volcano erupts, Musashi is caught in the smoke with the others and passes out. When he comes to, the Ōu dogs are in a shed in the mountains, saved by Jinemon Kurohabaki. They stay there until rescued by Daisuke and Hidetoshi. Musashi follows the group back into the mountains to find Weed. They participate in the final battle Masamune Kurohabaki against the packs.
Musashi is among the dogs who hear Gin howling, rallying them all to the top of a hill away from the attacking bears. Musashi assists the others in fending off the bears, and is saddened to find his old friend Jaguar crushed under Monsoon's paw. He continues to fight the bears until Monsoon demands to see the older dogs. Musashi claims he was born a fighting dog and so is ready to die at any moment for his friends. Jerome attacks Monsoon, followed by Musashi, but Monsoon prepares for this attack and slashes at the fighting dog, piercing his claws through Musashi's side and back. Monsoon flings Musashi off his claws, and the fighting dog dies from his injuries shortly afterwards.