Nah author, fuck you, you don't just get to gloss over "we made an arrangement with the hotel that this door can only be unlocked from the outside". This ostensibly takes place in real-world Japan; no architect nor PR firm would allow a hotel open to the public to be designed in such a way that doors could only be unlocked from the outside. They would be opening themselves up to MASSIVE lawsuits.
In short, based on what this manga presents (non-sensical legal situations, and gravity defying tits), I am forced to conclude that this is clearly a science-fiction manga.