Rin Ōtomo commanded the 15th Integrated Task Force of the Japanese Ground Defence Force, serving alongside her husband Itsuki Otomo and comrade Teppei Sugo. The unit operated as a close-knit military family, with Rin maintaining strong bonds among all members, including Sugo. During the classified Operation Foot Stamp in the Southeast Asian Union, Itsuki perished in combat when the Japanese military deployed unauthorized nano-based VX nerve gas, eliminating the entire ground squad. Rin subsequently took extended leave, a decision scrutinized in later investigations. Upon uncovering evidence that Colonel Yoshito Takaesu and Admiral Monto Minatoya concealed the bioweapon deployment and Itsuki’s true cause of death, Rin orchestrated a drone terrorist attack on the Japanese Ministry of Defence. She framed the deceased Itsuki by programming an android replica with his likeness and memories to execute the assault, seeking vengeance for the cover-up. Rin later raided Nago Base to assassinate Minatoya and Takaesu. During the confrontation, Takaesu ambushed her using a drone decoy of himself. Distracted by the decoy, Rin was shot and killed from behind by Takaesu, halting her direct revenge. Her death and the exposed military misconduct precipitated Teppei Sugo’s mental decline, ultimately leading to his recruitment as an Enforcer in the Public Safety Bureau.