Event Finale: The Spoils

Good job, girls!

Now that you've found the treasures, all that remains is to open them!

And that, of course, might not be so simple!

Ryuu-nee, would you mind going first?

Bring it on!

Great! First, please take out the key from the previous puzzle.

Hm? I don't think I got anything there?

Check your back pocket.

(Ryuuko takes out a handwritten note from her pocket.)

Huh? How... when did you put it there?

Hehe.

And here's the puzzle! Good luck!