Shikotsumyaku is a kekkei genkai of the Kaguya clan, allowing the owner to fully control the structure and growth of their own bones. The bearer of this ability controls three processes: osteoblasts, responsible for creating bone tissue, osteoclasts, which destroy it, and calcium density, which determines strength. As long as the body is not physically exhausted, bones can be grown in any part of the organism without restrictions.
In battle, the user instantly forms bone blades, spikes, drills, and entire plates, piercing the skin and extending them outward for attack or defense. Bones can be made hollow for special purposes or compacted to such a degree that they can withstand a direct blade strike. If necessary, they are fired from the body like projectiles. Extracted bone is replaced by new bone almost instantly, and torn skin heals at the same speed. This innate versatility turns the bearer's body into a living fortress and weapons arsenal simultaneously, which is why the Kaguya clan considered themselves invincible.
