Steel Release: Impervious Armour

This technique allows the user to turn their body into black steel, making that part invulnerable. Hiruko states that blades do not affect him at all due to this ability, proving this by using it to counter Sai's tantō, causing it to snap clean in half on impact.

Trivia

 * The portion converted into black steel is similar in appearance and functionality to Kakuzu's Earth Spear technique, though Hiruko did not show the offensive usage.