In an alternate reality where the Japanese government has retained state control over train lines, the Japanese National Railway (JNR) remains a safe and strong sector of employment.

Longing for a life of stability and security, train enthusiast Naoto Takayama enrolls with the JNR in the hope of becoming a conductor. Assigned as a trainee for the Railways Security Force, he’s tested on more than locomotives, and is expected to handle all potential threats.

Placed in the Fourth Guard Team, Takayama must be ready to handle any issue related to the functioning of the railways. His eccentric partners are the acrobatic misandrist Aoi Sakurai, brilliant prodigy Haruka Koumi, and routinely famished Shou Iwaizumi. Pitted against petty crime, infrastructural challenges, and the political extremists of ''RJ,'' the Fourth works day and night to ensure the success and prosperity of Japan's rail network.