Set 10 years after the original Full Metal Panic!, Ichinose Tatsuya is a normal high school boy living with his dad and little sister, Yukari. He has a history of falling for foreign women, not that it has ever worked out for him. One day, out helping with his father's company by driving a Power Slave, he runs into a beautiful foreign girl named Adelina….with the latest secret military-grade Arm Slave called “Shadow”, with her. What’s this highly armed and dangerous girl doing up in the middle of nowhere? Tatsuya is going to find out why very soon….