Akaya Kirihara is a second-year student and the youngest regular on the prestigious Rikkai Dai tennis team, earning him the nickname Junior Ace or Second Year Ace. He joined Rikkai with the ambition of becoming Japan's number one player, but his confidence was crushed by the team's three strongest members—captain Seiichi Yukimura, vice-captain Genichirō Sanada, and Renji Yanagi—which fueled a new goal to one day surpass them. Off the court, Kirihara appears childish, cheerful, mischievous, and somewhat naive, with a famously poor sense of direction that leads him to get lost easily. On the court under pressure, he undergoes a dramatic transformation, entering a state known as Devil Mode or Bloodshot Mode, where his eyes turn red, his aggression spikes, and he begins aiming powerful shots directly at his opponent's body. In its most extreme form, his skin darkens and his hair turns white, though this state also drains his stamina and mental control. Later, he achieves an Angel Mode that grants him enhanced control without the accompanying insanity, as well as the Muga no Kyōchi, a state of self-actualization that allows him to instinctively copy techniques he has witnessed. His signature serve is the Knuckle Serve, pressed between his knuckles and thrown with unusual spin. Kirihara has a close bond with Yanagi, who mentors him and once forfeited a match to let him advance, while Sanada disciplines him harshly with the intention of grooming him as Rikkai’s future captain. During the U-17 World Cup, he sneaks into the German team’s village and is caught, famously declaring, Akaya Kirihara, 14 years old, currently in trouble. His development includes learning to work in doubles, notably with Kuranosuke Shiraishi, who helps him keep his devil mode in check.