Yona is a member of the Knights of the Ashen Flame's Commando Unit.
He is a Third Generation, giving him the ability to ignite and manipulate flames from his palms and fingers. He can use his Ignition Ability to change the appearance of people's faces. He executes this process by using heat to control the blood flow in people's faces, and makes the capillaries and lymph nodes expand, and then uses localized edema to change the shape of people's faces, something he commonly calls art. He is also able to change his own appearance with ease. Using this same process, he can increase the temperature of someone's blood until they explode. Due to his age, it is speculated Yona is a non-human entity like the Preacher who does not age.
(Source: Fire Force Wiki)
