Erwin, legally named Riko Matsumoto, commands the Hippo Team’s German Sturmgeschütz III as both tank commander and radio operator. A second-year Ooarai Girls High student and history buff specializing in European WWII military tactics, she adopts an alias and persona mirroring Field Marshal Erwin Rommel, evident in her Afrika Korps jacket, German Field Marshal’s cap, British goggles, and fennec fox-styled haircut—a tribute to Rommel’s “Desert Fox” moniker. Standing 158 cm, she sports short blonde hair, brown eyes, and knee-high Marschstiefel boots. In sensha-dō matches, she dons Ooarai’s uniform but retains her cap and bow-tied neckerchief. Born June 18, her birthday aligns with Churchill’s “Finest Hour” address and de Gaulle’s resistance proclamation. Confident and tactically bold, Erwin displays a swaggering demeanor that falters only under intense stress. A staunch advocate for historical precision, she vehemently corrects misconceptions about the StuG III’s Winter War achievements and Finnish allies. Her leadership shines through inventive maneuvers like the “Napoli Turn”—a 180-degree spin while reversing to engage pursuers, honed from prior combat experience. She bonds closely with Yukari Akiyama, dubbed “Guderian” after the famed German general, collaborating on reconnaissance missions like their Pravda match scouting. Manga spin-offs expand her roles, showcasing adaptability as a Renault B1 bis loader and radio operator alongside first-years like Aya Ōno. Though her historical acumen guides terrain assessments and tactical recalls, strategic briefings are often delegated to teammate Caesar, reflecting a cooperative command structure. Additional trivia highlights her favoritism toward cornflowers and the Jagdpanther tank. Beyond main-series appearances, manga narratives further cement her versatility and reliability, weaving military history homages into sensha-dō’s competitive fervor.