Appearance
Personality
Abilities
Stand
Rock Physiology
While similar to a human's, their bodies can presumably change into rock. Because of this, they does not need to sleep or rest. They can mimic rocks to the point that it makes them indistinguishable from them.
Norisuke theorizes that Yotsuyu's physiology requires him to have at least a small amount of skin respiration and in the absence of such his body structure will begin to break down due to it becoming less structurally stable than an ordinary human's. This could be a trait shared by other Rock humans, including the A-un twins.
Synopsis
The pair are first observed performing tricks with a football in the streets of Morioh as Josuke and Karera walk on, to the amazement of the gathering crowd.
Later on they are again seen seated in a cafe where Karera steals their wallet and uses their credit card and her Stand power to obtain money she goes on to spend in a shopping spree. As the two walk away the twins can be seen questioned by a pair of policeman as to the strange nature of their ball and what one officer perceives to be a rock held in the hand of the older brother. When he demonstrates his Stand in subduing the policemen dialogue exchanged between the two brothers suggests that they have been hunting Karera and are surprised she has lasted this long.
Searching the streets for people who have come into contact with Sakunami, they eventually run into her and Josuke when the pair are nearing Kira's apartment, and the younger brother acts as a distraction while the other grabs Karera from behind and uses his Stand to transport the fuel in a car's tank all over her, proceeding to set her ablaze if not for the intervention of Josuke's Soft and Wet.
At the realization that Josuke appears to be a more pressing threat they decided to prioritize him as their target while allowing Karera to escape, more fixated on discovering the identity of the strange and powerful man who also has a ties to the Rokakaka Tree.
Trivia
References