Soshite, Dare mo ga Uso wo Tsuku (Volume)

is the first volume of the Soshite, Dare mo ga Uso wo Tsuku light novel series, written by Nozomi Mizukaga and Illustrated by Tea. It was released under the Dengeki Bunko Imprint in March 2011.

Synopsis
A mysterious boy, Adelbert, and his little partner, Ticca, board the huge luxury liner "Titan". The ship is full of unique people, including adventure merchants across the world, bewitching actresses, beautiful mysterious women and their companion newspaper reporters, and the enormously wealthy Marquis. It seemed that he was enjoying the trip. Adelbert himself was thrilled to travel with Lira, the daughter of the Gracieheim family, whom he met on this ship. However, in the meantime, the atmosphere of the trip changes completely when the death threat of "getting a blue diamond" arrives from the phantom thief Senin who is aiming for the jewels owned by the Gracieheim family. And-.

(source: Amazon JP - Translated)