"Shūmatsu Train Doko e Iku?" is set in a post-apocalyptic world where humanity has been decimated by a mysterious catastrophe. The remnants of society are scattered, and the few survivors struggle to navigate a desolate landscape. The narrative centers on a group of individuals who board a mysterious train that travels through the ruins of civilization. The train, seemingly autonomous and devoid of a clear destination, becomes a microcosm of the survivors' hopes, fears, and struggles as they search for meaning and a place to call home.

The main characters include a diverse cast, each with their own backstory and motivations. Among them is a young woman named Akira, who joins the train in search of her missing sister. Her determination and resourcefulness make her a natural leader within the group. Another key figure is Ren, a former engineer who harbors guilt over his inability to prevent the catastrophe. His technical skills prove invaluable as the group faces various challenges aboard the train. Additionally, there is Yui, a mysterious girl with no memory of her past, whose presence raises questions about the true nature of the train and its purpose.

As the train traverses the wasteland, the passengers encounter other survivors, some of whom are hostile, while others offer fleeting glimpses of hope. The journey is punctuated by moments of tension and camaraderie, as the group grapples with external threats and internal conflicts. The train itself becomes a symbol of both salvation and entrapment, as its passengers wrestle with the uncertainty of their destination and the possibility that it may never arrive.

The series explores themes of survival, loss, and the resilience of the human spirit. The characters' interactions and evolving relationships drive the narrative, as they confront the harsh realities of their world and the moral dilemmas that arise in their quest for survival. The train's enigmatic nature and the fragmented glimpses of the outside world create a sense of mystery and urgency, propelling the story forward. Through its blend of character-driven drama and post-apocalyptic intrigue, "Shūmatsu Train Doko e Iku?" offers a compelling exploration of humanity's struggle to endure in the face of overwhelming adversity.