Erich von Rerugen, a disciplined military officer from *The Saga of Tanya the Evil*, transitions into the parallel school world of *Isekai Quartet 2* as a teacher, adapting his strategic acumen to the crossover’s comedic setting. His analytical mindset and professional composure remain central as he navigates classroom chaos, balancing his tactical expertise with the absurdity of school life. Tasked with mediating conflicts between students from disparate franchises, he strategically intervenes in cross-franchise tensions—such as detaining Albedo during class to prevent her from disrupting Tanya and Ainz’s private exchange. Drawing from his background as a high-ranking Imperial General Staff officer, he enforces order with methodical precision, even when reluctantly taking the stage at a talent show to perform the Empire’s national anthem, prioritizing duty over personal discomfort. As a disciplinary committee member alongside Tanya and Demiurge, he upholds structure among the eclectic student body, reflecting his ingrained military discipline. Though the crossover simplifies his original narrative—omitting promotions, wartime strategies, and layered tensions with Tanya—it retains his wary vigilance toward her unpredictable antics, subtly echoing their fraught dynamic from their home series. His role remains confined to secondary authority within the school hierarchy, adhering strictly to his duty-driven persona without expanding on his broader backstory.