Kenji Asuka, who transforms into Midoranger, is a central character from the series Himitsu Sentai Gorenger. At seventeen years old, he holds the distinction of being the youngest member of the Gorenger team, a fact that significantly shapes his interactions and role within the group. His background is rooted in tragedy as he was a cadet training at the Kansai branch of the international espionage organization EAGLE. During a devastating assault launched by the terrorist Black Cross Army, his entire branch was wiped out. Kenji survived this attack purely by circumstance, as he was tending to pigeons in a hut on the rooftop at the time of the gas attack, leaving him unharmed while his comrades perished. This event led to his recruitment by Commander Gonpachi Edogawa, alongside other survivors from different branches, to become a member of the secret squadron known as the Gorengers.

As the youngest member, Kenji possesses a personality that is largely carefree and happy-go-lucky, though he can also display a brash and temperamental side. This youthful energy is a defining trait, and his fellow teammates often affectionately refer to him as baby or boy, acknowledging his status as the mascot of the group. He harbors a deep love for animals and nature, a characteristic that not only saved his life but also grounds his more spirited nature. Despite his occasional impulsiveness, his fighting skills are excellent, and he demonstrates a particular proficiency with speed-based combat, using his agility to full effect in battle. His motivation for joining the Gorengers is clear: to avenge the destruction of his branch and fight against the evil forces of the Black Cross Army to protect the world. He matures throughout the series, with early failures due to overreacting in his behavior gradually shaping him into a more adult and reliable warrior.

Within the team dynamic, Kenji holds the designation number 5. He shares a particular bond with his teammate Akira Shinmei, the Aorenger, who often looks out for him. He also enjoys playful interactions with Daita Oiwa, the Kirenger, occasionally posing riddles for him to solve. As Midoranger, Kenji is equipped with a specialized arsenal that reflects his agile combat style. His primary and signature weapon is the Midomerang, a razor-sharp, boomerang-like blade that he can throw at distant enemies or wield as a hand-held slashing weapon. This weapon is later upgraded to the New Midomerang, which features a slightly larger size. He also carries the Mido Puncher, a unique slingshot-style weapon capable of firing pachinko ball pellets and, on occasion, small explosives. For mobility, he rides a supercharged motorcycle called the Green Machine, which is eventually replaced by a new model known as the Green Star.