Boswellian

The Boswellian (ボズウェリアン,) is a special passenger ship.

Description
The ship is used by distinguished visitors sometime during the conference of country ambassadors and VIPs to discuss the Supranational Armed Defense Force. It consists of several rooms where each country ambassador's guards stay.

At some point, Ryunosuke Akutagawa infiltrated the ship and disguised himself as a crew member. Later, Ōchi Fukuchi, Ranpo Edogawa, and Atsushi Nakajima infiltrated the ship to hide in it from its erstwhile destination, the Yokohama Sea, to its arrival point.

The ship, specifically its deck, later turned into a battlefield for Atsushi's and Akutagawa's fight with Fukuchi.