Musashi Kazama begins as a young boy living in Tokyo with his father. His mother departed three years earlier, but he clings to the belief she will return. This situation forces his relocation to the countryside, a move he deeply resents. He fears his mother won't find them there and begs his father to return to Tokyo.

His perspective shifts dramatically upon meeting Jim, a man fishing for bass with a lure. This introduction captivates Musashi. Through Jim, who becomes his mentor and guardian, Musashi learns fishing techniques and discovers his maternal grandfather, Genji Takegami, was a legendary bass fishing champion called the "King of Granders." This revelation sparks hope that pursuing fishing might lead him to his mother. He displays a natural talent for lure fishing.

Fishing fosters Musashi's profound appreciation for nature. He forms close friendships with classmates Mio and Suguru. Suguru serves as the group's lure mechanic and expert, often crafting lures for Musashi and others. Mio provides steady support and companionship. The trio embarks on global fishing adventures targeting extraordinary and elusive fish species.

His primary fishing equipment evolves significantly. He first uses the Grander Tackle, a rod obtained early that uniquely restores nature, demonstrated in a key event concluding his initial adventures. This rod later evolves into the more powerful Giga Blade. Musashi employs specialized lures including Skeleton, Skeleton G, Orckaiser (and its upgraded form King Orckaiser, obtained after getting the Giga Blade), Legender Hawk, Legender Shark, and God Legender.

In a subsequent major quest, Musashi, accompanied by Mio and Suguru, travels the world seeking seven legendary, wish-granting artifacts called Legenders. These fish-shaped objects possess fantastic elemental powers and grant the power to change the world to those who catch them. Musashi specifically seeks Legenders like the Hawk Legender, performing optimally in sunlight and featuring sharp hooks, and the God Legender, recognized as the most powerful Legender, capable of catching any fish under any conditions and controlling other Legenders.

This quest is fiercely competitive. Musashi faces several rival fishermen also pursuing the Legenders: BB, a nature-protective girl wielding the Dragon Legender; Carl Amann, a hot-tempered individual initially indifferent to nature who eventually obtains the Shark Legender; Yun, a deceitful loner who learns to value friendship and earns the Scissor Legender; Masatsugu Hattori, an honorable ninja descendant dedicated to protecting nature who secures the Spider Legender; and Kuki Jr., the ruthless son of Musashi's former mentor/enemy, who initially gains the dangerous Devil Legender. Kuki Jr.'s change of heart transforms this lure into the Angel Legender.

Musashi possesses a strong sense of fair play and honorable conduct as a fisherman. He deeply cares for nature, akin to BB and Hattori. While enthusiastic and passionate about fishing and competition, he can be impulsive and occasionally reckless with lure use, often acting without thorough forethought. His experiences, particularly understanding his Legenders more deeply, contribute to his growth. His friendships, especially with Mio and Suguru, are central to his character.