Barely out of custody, Chiharu and Makina received their sentence: a thorough cleaning of the Milky☆Subway. The task seemed straightforward enough.

For their rehabilitation, Chiharu and Makina take a train to perform cleanup work. Joining them are four individuals who appear decidedly unwilling participants, it evident they hadn't volunteered for the task ahead.

The Milky Subway commenced its unexpected journey with six inmates concealed within its carriages. Earlier, during questioning, fissures began to appear in the composure of Chiharu and Makina—and Officer Ryoko began to perceive a patter…

Chiharu and Makina sprint toward the lead carriage, their goal to halt the derailing train – only to collide with the biker pair, Akane and Kanata. An uneasy alliance forged out of necessity, they continue onward, propelled directly int…

With Akane and Kanata now part of the team, the crew pressed onward. However, a dubious security bot stood in their path—and it showed no inclination for compromise.

The memory returned, sharp and unwelcome: the hours preceding the launch, when cyborgs Kurt and Max were questioned by Officer Ryoko. A disquiet lingered in the air, a subtle discord that defied easy explanation. What was amiss remained…

The group strained, attempting to bypass the malfunctioning security automaton. Their sole chance lay with Kurt and Max. Unfortunately, the two were profoundly averse to collaboration.

With Kurt and Max at last joining their ranks, the unlikely group of six pressed onward, only to find their progress abruptly halted by a sudden need for a restroom.

A sudden system failure sealed the train's fate, trapping its passengers. Chiharu found herself wedged in the women's restroom door, while Kanata, Kurt, and Max began devising a risky plan for escape.

Confined to the train’s cramped restroom, the team’s survival hinges on Kanata. Will he be able to rescue his companions—and perhaps gain the respect of Akane, who once dismissed him with a cutting remark?

The revelation is undeniable: the train is under the control of O.T.A.M., the conductor's artificial intelligence. Why does it sow discord among the inmates? And what enigmatic link connects it to Makina?

Cornered, the unlikely group confronts their ultimate trial: a desperate struggle unfolding within the confines of a deranged train.