When an unknown Arm Slave surfaces somewhere in the Taiwan Strait near mainland China, MITHRIL orders Melissa Mao and her team to go into a divided Hong Kong to investigate the perpetrator of the unknown Arm Slave. As the team continues to check into the reports of the unknown Arm Slave, the culprit is believed to be a potential SRT recruit back from Sousuke's training days in Belize when he was not recruited by MITHRIL.

Basically, it's a retanking of some chapters from Full Metal Panic!. It's sort of like FMP! Fumoffu.. meaning that there's no mecha plotline, only short stories. Also there's an extra story not presented anywhere in each volume of this series.

Following the Tuatha de Danaan's seajacking incident, things are back to normal at Jindai High School in Tokyo, or as normal as they get with Sousuke guarding Kaname. After finding out who betrayed Mithril and caused the seajacking incident, Kurz and Mao are sent on a top secret mission in order to capture and bring the traitor back.

However, Sousuke and Kaname's lives are about to change when they meet Leonard Testarossa, a high ranking member of a mysterious group named Amalgam. After their meeting, Leonard warns her that he would do anything to recruit her even if it means war in the streets of Tokyo.

From ADV:

Sosuke has finally lost his mind - and his memory! Rehashing his previous exploits will keep Kaname busy, but it doesn't take long for the military mind of this soldier to bounce back with a bang - literally! He's locked, loaded, and back to his old self by first period, as bombs and bullets grace the halls of high school!

From ADV:

Trouble always seems to follow the beautiful and sassy, Kaname Chidori. Though she is only a high-school student, Kaname is constantly the target of terrorism. Lucky for her though, the dreamy Sosuke, an undercover agent from Mithril, is one step behind her, ready to protect her at any cost. But will he be able to save her from harm every time she is in trouble?

The "slapstick drama" begins with Seiya Kanie, a high-school boy who is invited on a date in an amusement park by a mysterious beautiful transfer student named Isuzu Sento. He is introduced to Latifa, a "real" princess and the park's manager, and is asked to be the acting manager of this "disappointing amusement park in the Tokyo suburbs."