Mai Tanuma is the daughter of prominent shamisen performer Ryuugen Kamiki and younger sister of shamisen prodigy Souichi Tanuma. She shares a childhood history with Setsu Sawamura and maintains a social media friendship with Yui Yamazato. Mai possesses dark-brown hair tied in a ponytail with a red hair tie, featuring curly ends and bangs framing her forehead, accented by dark-brown eyes.

Mai harbors significant jealousy toward her brother Souichi and Setsu due to their exceptional shamisen abilities. Though skilled herself, she perceives her talent as inferior, fueling a persistent drive to surpass Setsu that deepens into an obsessive rivalry. She resents Setsu for declining a childhood competition he scarcely recalls, intensifying her competitive fixation. Her musical approach emphasizes technical precision and creativity, contrasting with Setsu's emotionally expressive style.

As a student at Umezono Academy, Mai competed in the Matsugoro Cup, achieving second place with her team. Her unique interpretation earned judges' recognition for its distinctiveness. She later serves as a shamisen instructor at the Kamiki school, reflecting her technical proficiency. Family dynamics reveal complexity: Ryuugen Kamiki is her biological father, while Souichi is her adopted brother. Her grandfather, Kouta Kamiki, adopted both siblings, intertwining their familial and musical bonds.