Sanpei Mihira
Voice - Masako Nozawa
A cheerful 11 year old who speaks with a distinctive Tohoku dialect and lives with his grandfather, Ippei Sanpei. However, when it comes to fishing, his eyes change, and he becomes a "fishing fanatic" who loves it more than anything else. He lives in a mountain village in Akita, surrounded by nature, and ventures out to explore different fishing spots.

Although his experience is still limited, he has a natural talent for fishing and earns respect from the adults around him. He often challenges himself by seeking out legendary fish and devises creative strategies to catch them. Throughout his adventures, he grows as a person while meeting various rivals and friends.

Ippei Mihira
Voice - Kohei Miyauchi, Masanobu Okubo (episodes 53+)
Sanpei's grandfather. He is a fishing expert and serves as Sanpei's mentor and surrogate parent, as Sanpei has lost his parents in childhood. He's also a skilled craftsman of Japanese fishing rods, known as Ippei Rods, which are popular among anglers. However, he prioritizes practical use over branding, once aggressively turning away a customer who requested a display rod.

After losing his grandson and daughter-in-law (Sanpei's older brother and mother) in a tragic accident, he was so heartbroken that he considered filling in the reservoir that claimed their lives. However, he realized that the reservoir also supports the lives of the villagers, and filling it wouldn’t bring them back. Instead, he vowed to raise Mihei to be a strong child who isn’t afraid of water, which ultimately led to the emergence of the fishing prodigy.

Gyoshin Ayukawa
Voice - Nachi Nozawa
A fisherman met at Crescent Lake during a fishing tournament, he is known as a wandering fisherman. They quickly form a bond, traveling together across Japan and beyond, with Sanpei looking up to him as an older brother. A skilled athlete and licensed lawyer, he wears sunglasses due to losing his right eye in a childhood accident. Although he’s the heir to the Ayukawa zaibatsu, he left home to escape his father's worries about his blindness.

He genuinely values Sanpei's talents but firmly admonishes him when he recklessly ignores safety while casting. He believes in letting Sanpei's skills develop organically, often refusing requests for additional instruction from others.

Yuri Takayama
Voice - Fuyumi Shiraishi
A girl two years older than Sanpei, she lives next door. They grew up like siblings and are childhood friends who bicker constantly. Sanpei calls her "Yurippe," and she calls him "San-chan." She lives with her father, Anzo, and her mother, Taka. She is hot-headed and moody. They have feelings for each other, but they don't seem to realize it. While her fishing skills aren’t the best, she once managed to win a tournament by chance.

Masaharu Kase
Voice - Keiko Yamamoto
A lively boy, around five years old, looks up to Sanpei as both a fishing and life mentor. Always striving to act older than his age, he draws inspiration from his grandfather, a respected net-casting expert in the area. As Sanpei becomes a master of fishing knowledge and techniques, this young boy often seeks answers from him, representing the audience's curiosity about the world of fishing.