Ishuu Benikawa commands the international postal airship Zanbani as its captain. She stands tall with fair skin, green eyes, and dark blue hair secured in a ponytail by a yellow ribbon. Her typical attire features a lavender crop top with diaphanous sleeves, a red sash over black skin-tight shorts, and tall brown boots, sometimes layered with a long green jacket. She wears glasses, once citing her age as the reason.

Strong-willed and independent, Ishuu harbors a fiery temper. She disciplines her crew with physical reprimands—hitting or slapping those she deems foolish or disobedient—yet intermittently reveals concern for their welfare. Her personal indulgences include spending spare funds on weapons and ammunition, frequent smoking, and drinking.

During crises, she makes swift, pragmatic decisions. Spotting government inquiry ships near Sentan Island, she immediately docked the Zanbani and dispatched scouts. She shows zero tolerance for insubordination, exemplified when Nakiami ignored orders to avoid Sentan Island: Ishuu waited furiously on the docks but displayed visible relief upon Nakiami's return.

Her relationship with Nakiami remains strained and complex. Ishuu has hurled derogatory insults at Nakiami and physically assaulted her, including repeated slapping after Nakiami disobeyed five years prior. Post-outburst, she often grapples with remorse through drinking and smoking. She permitted Raigyo Tsunomata, rescued alongside Nakiami by Ahm, to reside on the Zanbani for three years before his departure.

In combat scenarios, she engages directly with tactical competence. When Akiyuki Takehara's Hiruko transformation drew a Humanform attack, she retrieved a rocket launcher to neutralize the threat. She initially refused Akiyuki's request to return to Sentan Island, condemning his ingratitude toward Nakiami for saving his life. After Nakiami intervened, she allowed Akiyuki to stay aboard but warned Nakiami of his inevitable petrification.