API Key is a key to use the external AI (OPenAI&aposs GPT-3) that is responsible for the game master function of this game.
Call the external AI once and developer needs to pay for it.
You can use it for free for the first 18 times, but you will be charged for each use after that.

[1] Get a free API key from OpenAI.
Access custom page and enter the API key, and you can play with it.
You can get the API key from OpenAI&aposs website.
The good sources of process is this article.

[2] Support developers.
Now developing for beta version for suppoerter, you don&apost need to use custom page.
Also, I&aposm developing feature that user can write own story and play it.