Pandora in the Crimson Shell: Ghost Urn Vol 13

From the Seven Seas Entertainment edition

BEACH BREAK! Captain Robert Altman, last seen facing off against Poseidon’s battle robot, Caduceus, has disappeared! Was he killed? Or does Poseidon have something even more sinister in store for him? Meanwhile, a trip to the beach for Nene, Clarion, and Phobos turns dangerous when a Korobase security bot possessed by Niko-chan goes haywire!

Source: Penguin Random House API