I defeated her in the minigame and got the code. In my game, it is 289 874.

After input, it does not work. I shall try to complete Faith's quest while awaiting the answer.

Thank you in advance!

Alright, I figured it out.
In one of the answers of the developer, it is mentioned that the codes refresh every time you open the game.
Meaning, that you can go into the gallery of Butt Sex Janken on Luna's tablet. Click through the dialogue until the code appears.
Hopefully, I have been of help to some of you.