[The path to the new world... Could the two cases be related? Is that what this is about? Are they looking for the Silver Key and Yellow Sign to open the path...?]

[He's closer now, he can feel it.]

...I'm going to ask you a question, Mrs. Yuuki, and you are within your right not to answer, as you well know.

Do the words 'Yellow Sign' or 'Silver Key' strike you with any familiarity?