How does the triangle rune clown magic trigger?

According to the inquiry, I know I like playing games.

1. Take the elevator to find the old cat owner at the archive point on the first floor of the first chapter of the castle, ask the owner related questions and get a key fragment.

2. Then walk along the hidden road in the middle below the four dancers and get three key fragments.

3. Find the blacksmith to fix the key, return to the castle, open the cell and start the boss battle at the archive point of final baking and sale.