The Ame-no-Darin was made to extract resources from the ocean floor, such as oil and veins of iron ore - the discovery of these resources in the deep Pacific being what transformed the Island Nation into a top resource superpower. The island was also used as the Island Nation's military reserves base, with plenty of fuel and ammunition. Its security was left to a certain self-defense PMC as far back as the construction phase.
When the self-defense PMC went rogue and instigated a civil war, under the direction of Ichirei Shikon, they took full control of the Ame-no-Darin, with its full extraction and refinement abilities being capable of giving them an endless supply of fuel and ammunition rather than the ninety days worth of standard reserves. During their occupation, a new model of Object was constructed in a workshop in the floating island.
An assault was carried out on the Ame-no-Darin by the PMCs Moss Green with support from Sky Blue, as well as the Objects Ningyo and Yuuhi. During the operation, the Legitimacy Kingdom's 37th Mobile Maintenance Battalion and the Baby Magnum interfered with the activities of the PMCs. Though the Ame-no-Darin was ultimately sunk, the Ame-no-Uzume had already been completed and launched.