In the Land of Leadale, Vol. 7 (light novel‪)‬

Cayna, Opus, and their three servants are enjoying a bit of rest and relaxation in the remote village when Cayna decides to upgrade one her items: the Pair of Eyes, which transmits footage remotely between two eyeballs. She intends to use it so that the villagers can see and hear things happening in far-off lands. In order to locate this exclusive function, Cayna must return to the Guardian Towers that her old friends left to her, and this time she’s bringing Opus and Siren in tow!