Arpeggio of Blue Steel, Vol. 17

Amidst the preparations for the National Maritime Institute of Technology's school festival, Takao and 402 make their way into the heavily guarded "Facility Number Four." Deep below the burned-out ruins of the facility lies a strange secret. Elsewhere, in order to protect the White Whale from an encroaching Fog patrol fleet, the crew of the I-401 creates a diversion, only to find themselves ambushed!