Su Matsuno presides over Ohgyoku Academy as its principal, placing her in direct institutional opposition to Ran Ookumo, who leads Kin'gyoku Academy. Their history spans roughly fifty years, beginning as close friends in youth. This friendship shattered due to a romantic rivalry over Saizo Igano, Kabamaru's grandfather and their former ninja instructor. The personal conflict over Saizo transformed their bond into a bitter, enduring rivalry that spilled over into their professional lives, crystallizing into a feud between their respective schools.

This deep-seated enmity between Su and Ran fuels the intense competition and hostility between Ohgyoku Academy and Kin'gyoku Academy, driving significant conflict within the series and shaping student interactions and institutional strategies. Their animosity endures even in their elderly years, underscoring the depth and resilience of a conflict rooted in unresolved romantic tensions and personal betrayals. As principal, Su Matsuno is a key figure perpetuating this feud through Ohgyoku's policies and engagements with Kin'gyoku. Her character epitomizes the consequences of a prolonged rivalry entrenched across generations.