Ken Nakajima serves as a motorcycle patrol officer at the Bokuto Police Precinct, a role that showcases his primary talent as an exceptionally gifted rider. His skills on a motorcycle are so advanced that he could likely pursue a successful career as a professional racer if he chose to do so. This expertise earns him the nickname White Hawk among his peers, a recognition of his abilities in chasing down offenders on the road. He holds the rank of Patrolman.

Physically, Nakajima is described as strong, tough, and handsome, a presence that is often accentuated by his police uniform and sunglasses. Despite this imposing exterior, his personality is marked by a stark and endearing contrast: he is terribly shy, particularly in personal matters. This shyness is most pronounced in his interactions with his fellow officer, Miyuki Kobayakawa. He and Miyuki share deep romantic feelings for one another, but both characters experience significant difficulty in expressing these emotions openly, leading to a relationship defined by unspoken tension and mutual awkwardness. His motivation is often tied to his duty and his quiet devotion to Miyuki, which can sometimes override his usual composure. In one instance, his concern for Miyuki's safety, after hearing a rumor about a curse endangering her life, drove him to take impulsive action, leading him to investigate a supposedly haunted warehouse on his own, where he was ultimately frightened unconscious.

In the story of You're Under Arrest: Full Throttle, Nakajima functions as a key supporting character. His most significant relationship is undoubtedly with Miyuki, which forms a central subplot of the series. He is also close with his father, Daimaru Nakajima, who owns a motorbike shop called Zapper. Daimaru, an expert on motorcycles and an excellent rider in his own youth, taught Ken his riding skills and continues to offer guidance, sometimes to an overbearing degree. Ken is the stepson of Sena Wakabayashi, his father's much younger, teenaged second wife. His family originates from Mie Prefecture. Throughout the series, his development is subtle, primarily revolving around his gradual, often fumbling attempts to bridge the emotional gap between himself and Miyuki, though he consistently struggles to move beyond his inherent shyness.

His notable abilities are centered almost entirely on his prowess as a motorcyclist. His riding skill is of a professional caliber, making him an invaluable asset in high-speed pursuits and a respected figure within the precinct for his operational expertise.