Niko Miyagi is a young man with a lean and athletic build, a testament to his years of rigorous training as the Ultimate Swimmer. Despite his impressive physical abilities, Niko is often reserved and introverted, with a tendency towards anxiety in social situations. However, when he is talking about swimming, his eyes light up and his confidence shines through. He is incredibly passionate about his sport, and his dedication to improving himself in the water is second to none. When faced with challenges, Niko may initially hesitate, but he never gives up on his goals and always strives to be the best swimmer he can be.

Niko Miyagi's voice is medium-high (young boy ish) and soft-spoken and gentle, yet carries a sense of determination and focus. Despite his shy nature, there is a sense of quiet strength in his voice that hints at discipline and dedication.