This pair of crystal glasses was given to Nausicaa by Angel when she left the Sky Mechanical City.
At that time, Nausicaa thought it was some secret weapon specially made by Angel to ensure her safety.
However, Angel denied it.
Nausicaa still remembers what Angel said at the time—
"This is not a weapon, and it's not very useful when you're in danger. However, if you need to inform me of anything, you can use this."
"So, it's a communication device?"
"You could say that, but it can only be used once, so use it wisely."
After getting this "communication device," Nausicaa kept it in her pocket, never having used it or even thought of using it. More often, this single-lens glass served as a token of her friendship.
Because the reality was much like what Angel said, it wouldn't help in the face of danger, and if there was no danger, there was no reason to contact anyone.
