This short game is perhaps the closest thing I can think of to a system-neutral storygame one-shot. The intent is clearly to play it as a sort of solo journaling experience, using a deck of tarot cards to help randomize the prompts you choose, but it could easily be turned into a duet experience with one player as the youngest mermaid venturing onto land for the first time and the other serving as a GM. You could even do something inventive and make a 5-player game out of it, with 4 people each taking on the role of one of the tarot suits and a mer-player choosing between them. It's a testament to the quality of the concise writing that I can easily imagine a number of different ways to play through this short game, each of which delivering a potentially radically different experience.
However you choose to play it, you're basically exploring Hans Christian Andersen's original Little Mermaid story as the titular character and building up to this game's titular choice: blood or foam? It's a violent and painful choice regardless of the actual outcome, and the delights of the night leading up to it will shape your view on both it and the rest of your mermaid's life. Choose wisely, but choose nonetheless.