Kai Tōdōin is a 15-year-old male student at Camelot Academy's Japan branch, ranking among the A-class elite. His strict, short-tempered demeanor and intimidating appearance contrast with a fiercely loyal and passionate core, especially toward his friends. Chronically low blood pressure leaves his legs weak, forcing him to skip morning training sessions. His unconventional fashion sense draws frequent notice. In golf, Kai lacks innate special powers but compensates through intense dedication. He achieves exceptional driving distances using specialized equipment, initially wielding a 55-inch driver to surpass 400 yards. His statistics include a 315-yard average drive, 1.7 putts per hole, and a personal best score of -7. During a high-stakes driving contest, he pushes past human limits with an 80-inch driver to achieve a record 446-yard drive, an effort that severs a tendon and ends his competitive career. Kai shares a deep, longstanding bond with childhood friend Mika Kuromine. Their mutual romantic feelings remain initially unspoken due to shared hesitance. After his injury, Kai transitions into club making and eventually marries Mika; the couple later has a son. Significant character growth defines Kai during the Camelot Cup. Initially dismissive of rivals, he gradually learns to acknowledge and respect the skills of competitors like Tristan Liones, Lancelot Norman, Charles Livingston, and Percival Lawrence. His courage crystallizes when he volunteers to challenge Momiji Sugagawa—a defining moment showcasing his willingness to confront formidable opponents despite personal risk.