Perrine-H. Clostermann, formally Pierrette-Henriette Clostermann, hails from Gallia as head of the noble Clostermann family and lord of Pas de Calais county bordering the Straits of Dover. Her family's fortune dwindled after she poured personal savings and military earnings into Gallia's reconstruction following liberation from the Neuroi invasion, which left profound emotional wounds. These scars initially fostered a rigid, aristocratic haughtiness and rejection of teamwork, fueling hostility toward newcomer Yoshika Miyafuji over Yoshika's bond with Mio Sakamoto—culminating in a formal duel challenge.
After Gallia's fall, she retreated to Britannia, fighting with the Britannian Air Force during a striker shortage. Upon equipment availability, she transferred to the Forces Aériennes Galliaises Libres 602nd Flying Corps, distinguishing herself as the "Blue premier"—an unmatched ace. Her admiration for Mio Sakamoto sparked after fifteen consecutive duel losses to her during this posting. Mio later alerted her to the newly formed 501st Joint Fighter Wing and its mission to liberate Gallia, prompting Perrine's reassignment.
Within the 501st, Perrine initially upheld her aloof persona, chastising uncouth habits like loud eating. She favored solo combat, wielding lightning-based Tonnerre magic that strikes multiple foes but frays her meticulously styled hair. This magic summons physical traits of her Chartreux cat familiar—ears and tail. She fought with a Bren light machine gun, occasional PIAT, and an ancestral rapier symbolizing family heritage.
Gallia's liberation catalyzed her evolution. She led Pas de Calais' reconstruction alongside Lynette Bishop and Amelie Planchard, converting her family estate ruins into an orphanage and school where she taught displaced children. This softened her demeanor toward community engagement. Intensive broom-flight training under Anna Ferrara during the Romagna campaign refined her magical precision.
Post-war, despite reluctance, she commanded Gallia's new 506th Joint Fighter Wing due to public demand. She sustained a deep friendship with retired Group Captain Rudel, restoring herb gardens in a memorial park—honoring her family's botanical legacy. Her Striker Units progressed from the Armurier de l'Aéronautique VG.39 to experimental VG.39bis and engine-enhanced variants, all retaining Britannian camouflage and her emblem.
Relationships included complex dynamics with Mio Sakamoto, shifting from idolization to fierce protectiveness, and rivalry-to-respect reconciliation with Yoshika. She held nuanced views of 501st comrades: respecting Gertrud Barkhorn's prowess while noting her reserve, acknowledging Erica Hartmann's aerial skill despite disliking her aggression, and tolerating Francesca Lucchini's antics while admitting her combat effectiveness.