Iburi Clan

The was a seclusive clan that lived underground in the Land of Fire. They had the ability to become smoke at will and still physically interact. However, this ability was imperfect, causing them to occasionally transform unintentionally. In their smoke form, they were vulnerable to wind as it caused them to disperse permanently and die. Because of that, clan members did not tend to have long lives, and were forced to live confined in caves or places where the wind is practically nonexistent. Instead of tombstones to honour the dead, the clan would instead plant trees for them, believing their deceased souls would watch over them. They were later found by Orochimaru, who used his cursed seals to partially stabilise their ability. Claiming he needed more research to perfect the process, the clan willing gave him multiple children as test subjects, as the ability is more pronounced the younger the user is. Ultimately, the entire clan, excluding Yukimi, was killed off by Orochimaru in an attempt to find a blood source capable of bestowing him with this power.

Trivia

 * means to smoke.