Thanks, I found it. Now that it was darker it was visible, but back then I couldn't really see it and even tried walking there blindly without success.
I'm stopping at the 4th key (or at least I'm assuming that's it). It's stays good all the way through and the production value is high, which could be surprising when compared to the pixel art style and even if it doesn't suit my general tastes. And there's smells like teen spirit outright being used, so I did get the musical reference right.
Just when I was going to complain about the amount of combat getting in the way of the plot, you give stuff to compensate and appreciate it, on top of having kino boss fights. The amount of equipment is insane too.
Shame found!
Good job on the game.