Han wears this Steam Armour (蒸気の鎧, Jōki no Yoroi) in order to use his steam-based ninjutsu. Along with covering his entire body, the armour contains a furnace in its back, where the steam is produced. The pressure resulting from this emitted steam can then be used to increase the force behind Han's physical attacks. The exact amount of force produced is proportional to the quantity of steam released, as the greater the volume of steam utilised, the larger the pressure that can be built up within the armour is. For example, when a significant amount was used, just a simple kick was capable of knocking both Naruto Uzumaki and Killer B, who only caught the former, a large distance away.
In video games it's also been shown that he can use the hot steam emitted by the armour to burn opponents around him.