The Impossible Stairwell is a Science Fiction novella by S Douglas Johnson. On the first day back at school after Golden Week, Etsugoya Jun'ichi notices a few odd events, like a note in his shoe locker that predicts a series of cards drawn from a deck, and a stairwell on the floor plans to his high school that should not be there. By going up and down the stairwell, he finds himself jumping forward and backward through time. Together with his classmate Tsubakihara Amaya, he tries to learn how the stairwell works, and uses it to make sure that the odd events happen as they did.
The Impossible Stairwell provides examples of the following tropes:
- Ascended Fangirl: Tsubakihara is a fan of Science Fiction.
- Our Time Travel Is Different: The instantaneous variant. Going up- or downstairs in the impossible stairwell takes Etsugoya forward or backward in time so subtly he does not even realize anything has happened at first.
- The Slow Path: Discussed as an option to avoid having to climb multiple flights of stairs.
- Stable Time Loop: The school and its time-traveling stairwell appear to be designed by a future version of Etsugoya Jun'ichi himself.
- Shout-Out: To Slaughterhouse-Five.
- Time Machine: the titular stairwell.
- Time Travel
- Time Travel for Fun and Profit: Etsugoya wins a bet with information obtained (without his knowledge at the time) from his future self. Later he and Tsubakihara briefly discuss the ethics of doing this.
- Time-Travel Tense Trouble: Both Etsugoya and Tsubakihara have some trouble before deciding to "just pick one tense and stick with it".
- Trust Password: At one point, Etsugoya and Tsubakihara write notes to themselves that they alone would recognize to test whether or not they are traveling through time.