Hidden away from the eyes of the ordinary world stands a hotel that is not found in any guidebook. To the casual observer, it may seem like a normal, high-end establishment, but its true clientele consists entirely of assassins. This is a sanctuary for those who have forgotten their humanity, a place where the Hotel Inhumans offers its guests not only luxury accommodations but also a dark suite of premium services: deep cleaning of weapons, secure identity fabrication, and the flawless disposal of corpses. The golden rule of this establishment, upheld by its concierges, is to never say no to a guest's request.

The series follows the daily operations of this unique hotel through the eyes of its two main concierges. The first is Hoshi Ikuro, a rookie staff member who is deeply uneasy with his surroundings. He dislikes blood and violence, often muttering that he wants to quit, but he remains on the job due to circumstances tied to his past—specifically, the murder of his mother by an assassin, which led to the hotel taking him in. His primary interest is cooking, a hobby that often proves useful. His counterpart is Haizaki Sara, a cool, collected, and incredibly capable veteran concierge. Unlike the hesitant Ikuro, Sara is a professional who prioritizes customer service above all else. She is also the hotel's strongest guard, possessing formidable combat skills that she uses to protect the hotel's secrecy and its guests without hesitation.

Beneath the veneer of a simple action story, the manga explores a series of episodic yet deeply woven human dramas. Each guest who passes through the doors brings a unique story, ranging from tragic to terrifying. A young man forced into killing to protect his captive sister, a professional leading a double life to hide his profession from his family, an emotionless girl raised as an assassin seeking purpose, or an elderly retired hitman suffering from dementia who checks back in with fractured memories of his past. The concierges, particularly the reluctant Ikuro, act as a bridge between the killers and the remnants of their humanity. As Ikuro navigates this world where death is business as usual, he is not just serving clients; he is journeying to uncover the truth about his own past and the reason he was brought to this place where one must confront the darkest depths of the human soul.