Rock Human

The Rock Humans (岩人間) are a race of mysterious beings that serve as antagonists in Part VIII: JoJolion.

Summary
The Rock Humans are a race of idiosyncratic humans whose original forms take on a "rock-like" composition. In this form, most biological activities come to a halt and they're able to endure high and low temperatures, dryness and other things in nature.

While they are generally represented as humans, Iwasuke, a dog of unknown origin, also appears to have similar abilities and is described as a rock dog.

Hibernation
Sleep hits suddenly at different times depending on the individual and will last anywhere from 30 to 90 days. While hibernating, breathing is halted, though a small amount of skin respiration is required through the cracks found on their outer layer. If necessary, they can stay in hibernation for 25 years and sustain temperatures as high as 950°C and as low as -240°C. Their body heat, as well as scent, disappear while dormant causing various fungi, moss and even pearls to grow on their body. The means by which they harden into stone involves an intricate cell system that stores moisture within the interior of each cell and is protected by carbon-rich cell walls.

When hibernating, Rock Humans will prefer places such as Shrine grounds, parks with statues, gardens of expensive houses, and underneath maple trees with squirrels in them. They will generally avoid sleeping in areas that were previously flooded, or have high chances of being rained on by tree sap or bird poop.

Biology
About 95% of Rock Humans are Stand users, there are both males and females and give birth. They also rarely fall in love with normal humans, but if they do, there's a 97.5% chance it will end in disaster. The breakups between humans and Rock Humans are said to end in the form of murder. Visually, there are no differences between them and humans, though their skin upon awakening appears slightly moist, damp and erotic.

Rock Humans do not grow gradually, but "molt" their whole bodies at once every 6 years. This transformation occurs during their sleep, and for some unknown reason, the pose they make when asleep will change each time. It is believed that Rock Humans can live for 240 years. When a Rock Human dies, it leaves no corpse, as it crumbles away into rocks.

Behavior
Rock Humans eat plants, fruits, nuts, meat, fish, and all other forms of life. They enjoy honey, but are all allergic to mangoes. They hold a certain reverence for the power found within the Earth and nature. Because they are fundamentally able to live through weather changes, they require no assets such as a house or land. However, they are unable to safely coexist or mutually understand human society. Because of this, some have taken the form of "parasites" by falsely entering the family registry system to maintain property and assets. However, due to their extensive hibernation, Rock Humans cannot go to school or hold a regular jobs, instead working in occupations that allow irregular business hours.

Abilities and Powers
Rock Skin: Presumably separate from hibernation, each Rock Man has the ability to shift their outer appearance from a normal human into a rock-like state and vice versa at will. In their rock form, they are able to camouflage into their surroundings, and improve durability to some extent. The ability to stay human requires some type of focus however, as Aishou describes his rock form as something he was born with, but unable to control at a younger age. Yostuyu, who is presumably more experienced in controlling it, is able to revert to human, rock, and a hybrid where he can still move despite having a rock-like appearance. This form can be used advantageously as camouflage or in Yotsuyu's case, can forgo the need for accommodation or food.

Trivia

 * The concept of the Rock Humans is similar to the Pillar Men in Part II: Battle Tendency.
 * It also may be in slight reference to minor Pt. IV antagonist Anjuro Katagiri, who literally becomes a "rock human" (a human fused with a rock) after his encounter with Josuke.
 * Although their motives are unclear, at this point in the manga the 'Rock Humans' are the collective antagonists of JoJolion.