Engraved Ring

Exploration Stage: Shooting Star Cabaret
From: Mr. Black
Description: I'm sure the singer's hiding a lot! Doesn't it seem strange to you that she has a cache, let alone one with such a tricky lock? I saw that she had an unusual drum ring, it should fit into the next section of the lock.
Completed: We have the drum ring. Look, there's an engraving on its inner side: "For my mysterious." It seems that Sophia uses it to turn the lock's relay. Look at that, it worked!