Deian Ishizu

Ishizu is greedy, elitist and possessive of his position within Yokohama's medical establishment. He sees expensive Western medicine as an investment from which physicians deserve substantial financial returns and has little sympathy for patients unable to afford treatment.

Elder's behavior consequently offends both his financial interests and his worldview. Her willingness to treat impoverished people for little or no payment demonstrates an approach to medicine fundamentally incompatible with his own.

Ishizu is also willing to employ intimidation and violence to preserve his business. Rather than compete with Elder through medical ability, he uses hired thugs and eventually a professional killer to remove her.

Ishizu is a trained physician familiar with Western medical practices available in early Meiji Japan. His position within Yokohama indicates considerable professional standing, particularly among wealthy residents and foreigners.

He is not an established martial artist and relies on hired men when physical force is required. His resources allow him to employ Espiral, a professional assassin considerably more dangerous than his ordinary thugs.

Ishizu also obtains smallpox material and intends to exploit an outbreak for profit, demonstrating both medical knowledge and an extreme willingness to weaponize disease.

Ishizu encounters Elder while she is treating an impoverished woman. He orders her to stop practicing medicine without his approval and makes clear that her free treatment of people who cannot pay interferes with the profitable medical system from which he benefits.

Kenshin intervenes when Ishizu's men threaten Elder's patient. Unable to remove the doctor through intimidation, Ishizu escalates the conflict by hiring Espiral.

After Espiral fails to resolve the situation, Ishizu attempts to release smallpox so that the resulting epidemic will create paying patients. Elder prevents the contaminated material from spreading, bringing his scheme to an end.

The 2023 anime adapts this conflict across its Act Zero episodes, retaining Ishizu's central role as the corrupt physician opposing Elder.

Elder Peaberry is Ishizu's professional rival. Her willingness to treat poor patients without prioritizing payment threatens both his profits and his conception of medicine.

Espiral Rotacion is the assassin Ishizu hires to eliminate Elder.

Kenshin Himura becomes Ishizu's enemy after protecting Elder and her patients from his men.

Dankichi Asahiyama works with Elder and openly opposes Ishizu's attempt to prevent her from treating impoverished residents.