Bone Growth

**Bone Growth** (骨成長 - Hone seichō) is a quirk used by Nankotsu Kotsuzui.

## **Description**

With his quirk, Nankotsu is able to generate manipulate the calcium inside his bones (dragging all of the other components along with it) to create bone-like structures around his body with the joints if joints are necessary, which also includes his teeth. To avoid hurting himself every time he creates a bone construct, his skin and muscle kind of automatically move out of the way so the bones can generate, which can lead to a few advantages, given the fact that in that area, there’s no nerves, meaning no pain, the bones can’t be burnt unless at a specific temperature (and even then he can just regenerate the bones unless it’s his entire body that’s getting cooked alive), and bones don’t become brittle or lose their integrity when frozen. Some other advantages to having this quirk is that he can fix any broken bones he has, and if he grows his limbs to make the skin move out of the way, he can detach his limbs and grow them back, however it will take at least around 2-3 weeks for the bone marrow to grow back in that limb thanks to him having mild control over said bone marrow. This is fairly fast, considering that it normally it takes 4-6 weeks for bone marrow to grow back.

### Weaknesses

Some limitations to his quirk is that the kinds of bones he can generate are limited to the bones that other animals have. If it doesn’t exist in the wild, he has to create multiple bone constructs to make the shape. For example, he can make scythe-like blades from his arms, since those are just rib cage bones but sharp, and antlers since things like deer and elk have them. He can’t, however, make something like an axe head on his arm, since there are no bones anywhere in nature that come remotely close to an axe head. If he wanted to make an axe head, he’d have to make the shape out of a whole variety of different bones. Some other limitations are that the bone constructs he creates are hollow since he can’t generate bone marrow (yet), only manipulate the bone marrow he has in his body, which even then takes a little bit. The bones also have to be connected to his body, meaning he can’t go full blown Megalovania on anybody without getting a little creative. Yet another thing he has to keep in check is his calcium levels, since you can't exactly create something if you don't have any materials to use. However, he can retreat his bone constructs back into his body, thus restoring his calcium levels.

## **Usage**

### Normal Abilities

Outside of combat, Nankotsu’s quirk doesn’t see as much usage compared to other quirks. Sure, he can fly with his wings (thus avoiding foot traffic), being able to grow more arms for utility, and being able to use sharp bones as knives, that’s honestly about it. Inside combat, however, is where this quirk becomes a Swiss Army Knife. As long as it’s a bone in a creature’s anatomy, than he can produce it. Rib cage bones are probably the most versatile, since they can be used to make something like scythe blades on his arms, ends on extra limbs to make spider-like appendages, be connected in a circular shape to make a shield, they can even poke out of his head to make demon-like horns. Along with that, he can enlarge his limbs, elongate them, basically whatever he wants to do with them.

### Ultimates

#### Bone Demon

When Nankotsu turns into this form, he grows his skeleton so that his skin and muscle move all the way to his back (which becomes a weak spot) that’s situated between his shoulder blades where he grows the skeletal structure of human-scaled bat wings, where he moves his bone marrow to create the wing membranes. He also generates a tail with a very sharp end to stab people, changes his foot structure to be able to carry people better, and small demon-like horns for aesthetics. In this state he’s essentially immune to pain, burning at a certain temperature, and freezing altogether all except in one spot, which is where all his skin and muscle are. However, to get to that spot, you have to get through a flying speeding skeletal demon that can easily stab you and fly circles around you. He does have to undo the growing bit eventually, since keeping all of his skin and muscle in one small space isn’t ideal, and will eventually try to stretch back over the bones. He can still use his wings and tail after transforming back, though.

(Image of him using Bone Demon)

##### Bone Demon Varient: Jersey Devil

After a trip to America, learning of the Jersey Devil, and a lot of training, Nankotsu learned how to create a faster and harder hitting, but more frailer variant of Bone Demon. After transforming into his Bone Demon form, his horns grow into antlers, his skull becomes more stag or horse-like while all his teeth become more carnivorous and serrated, and his legs and feet transform into a leg structure commonly seen on horses, goats, deer, and the like, hooves and all. His ribcage, which used to have all of the gaps filled to protect his organs (Some of which like his intestines and kidneys were pushed up into that protective area), have those gaps removed, which while it does allow him to have more material to have stored for other uses and makes him a bit faster, it does obviously leave his organs wide open for attack if opponents can land their attacks in between his ribs.

#### Bone Colosseum

Nankotsu grows a large, bulky tail that can support his body weight and stabs it into the ground. He then grows bones from the tip of the tail underground to create a circular area from under him that is around 14 feet in diameter. At the ends of those bones, Ribcage bones shoot up to around 15-20 feet from the ground, creating a circular wall and trapping anyone within that 14 foot diameter. Then, from where the ribcage bones touch the ground, he creates a bone flooring that comes back to where his tail is, which is at the center of this new colosseum like structure. Nankotsu now has total control within the Colosseum, allowing him to go full-blown Megalovania on his opponents. The other thing is that the tail will keep Nankotsu airborne by staying upright and will keep him away from very close range attacks and those who can't get to his height. This does come with some fairly obvious setback, however. While he's growing the colosseum, he can't move from where he is, making him vulnerable to attacks. While the colosseum is generated, he, once again, cannot move, meaning those that can get to his height have easy access to him. With generating such a big structure, that reduces his calcium levels by a lot, leaving the task of protecting his body to mostly his original skeleton if he wants to keep up the spikes that he'll be generating.