Having qualified for on-the-job training, Naoto is assigned to K4, the Tokyo Central Railway Security 4th Guard Team. Waiting for him there are his partners from JNR Central Academy: Aoi, Haruka, and Sho. They immediately set about their work at Tokyo Station, but as if being teamed up with the gruff Aoi didn't worry him enough, Naoto is increasingly anxious as he watches the Tokyo Public Security Mobile Police set out on a mission.