Mystery! Nakajima's Double / The 20-year-old Girl is His Mother.Episode 16 Mystery! Nakajima's Double: Natsumi and Miyuki encounter a motorcyclist wearing sunglasses resembling that of Ken. Gossips and rumors spread about Ken quitting the police department to become a professional racer. They cross paths with the motorcyclist a second time in a line of traffic. Ken is able to catch up to him, identifying him as Daimaru Nakajima, his father. Daimaru mistakes Natsumi for being Ken's girlfriend, much to Miyuki's shame. Later on, Natsumi tries to convince Miyuki to admit for feelings for Ken in front of Daimaru, only to turn out unsuccessful. Natsumi then tries to persuade her to show Daimaru her driving skills in her car. Coincidentally, another biker shows up to race against Daimaru. Daimaru is very impressed to see Miyuki tailing him, however he loses concentration, resulting in injury. While Miyuki treats his wound, he ultimately decides to accept her relationship with Ken.
Episode 17 The 20-year-old Girl is His Mother: Natsumi and Miyuki are welcomed by Sena Wakabayashi, a women from who is twenty years old, who explains that she will soon be Ken's stepmother. After Sena drops Ken to the precinct, gossips and rumors spread concerning his relationship with her. Sena later comes back to deliver lunch to Ken, causing further embarrassment. Natsumi and Miyuki offers Sena to spend the night at their house. Sena recalls falling in love with Daimaru when she first encountered him on a mountain pass. Miyuki suggests Sena to take Ken on a shopping spree. Ken is disturbed by having Sena as his mother, only thinking of her as a little sister. Miyuki and Ken stay behind to tend to Sena, who has been run over by two guys who have stolen her car, while Natsumi and Daimaru barricade the two guys.