Kotetsu, a katana tsugumomo forged with the essence of "tiger" (虎) and "iron" (鉄), transitioned from serving Suou Sumeragi to partnering with Sunao Sumeragi, a malison cleaner born into exorcist lineage. Initially dismissed as a mere weapon by Sunao, his tactical insights were routinely ignored in battle, her pride prioritizing familial prestige over collaboration. This imbalance culminated in their duel against Kazuya Kagami, where Sunao’s refusal to heed Kotetsu’s warnings fractured his hilt, rendering him unusable and exposing her vulnerability. Defeat forced Sunao to reassess their dynamic, shifting from viewing Kotetsu as a tool to embracing him as an equal partner. Though their alliance strengthened, her tsundere disposition and lingering pride occasionally reignited friction. Beyond combat, Kotetsu embodies the interplay of cooperation and respect between tsukumogami and wielders, a theme central to their narrative. His enduring role in arcs like the Reversal Arc highlights his sustained relevance to Sunao’s growth. The shattered hilt remains a stark emblem of her past hubris and the fragile equilibrium required in their bond, underscoring transformation without erasing its complexities.