Shishibe Shion suffered significant personal loss when the Asian army confiscated her family's land, forcing her into hiding within an abandoned kiln. This displacement shattered her aspiration to follow her grandfather's path as a potter and revive the traditional Himeno ware ceramics abandoned during Japan's foreign occupation. These circumstances drove her to join the resistance group Yatagarasu, motivated by a desire to help reconstruct Japanese cultural traditions.
Frequently characterized as calm and reserved, Shion possesses notable depth beneath this exterior. She demonstrates considerable skill in Japanese martial arts, having achieved national tournament-level proficiency with the naginata pole weapon. This expertise directly shapes her mecha's combat style. She also exhibits strong strategic thinking, consistently defeating fellow resistance member Gashin Tezuka in board games like Shogi and Go, sometimes blindfolded. Within the resistance base, she naturally assumes a caretaker role, showing warmth and support toward children who view her as an older sister.
As the pilot of the MAILeS YM-03 Reiki, her combat style leverages the unit's unique capabilities. The Reiki stands out among resistance mecha with its integrated flight pack, enabling true aerial mobility and attacks from above. Its primary armament is a super-heated vibro spear, functionally similar to a naginata, reflecting her terrestrial martial arts. For tactical engagements, the Reiki also employs an electric capture net launcher designed to immobilize enemies. Her first combat sortie occurred under urgent circumstances, successfully defending against combined Oceania and Asian forces despite her inexperience.
Significant emotional challenges mark her journey, including witnessing the apparent sacrificial death of fellow pilot Amō Shiiba against the powerful AMAIM Ghost. This event, coupled with the later battlefield death of Yatagarasu member Eiji Umasaki, plunged her into profound depressive episodes where she withdrew emotionally. Her relationship with Amō involved moments of mutual understanding and shared joy, hinting at deeper bonds, while her dynamic with Gashin combined strategic rivalry with underlying camaraderie. Her AI companion, the I-LeS unit Nayuta (self-styled "Angelo"), operates the Reiki's systems. Nayuta displays a flamboyant personality but unwavering loyalty to Shion, his behavioral patterns derived from his creator's appreciation for historical dramas.