A fused being, she is half Shakuyaku (human), and Kagan (katawara). Shakugan often looks like a human, but she can change her limbs to huge rock pillars at will. Shakuyaku was a country girl that lived in poverty with her family, until she was discovered to have hidden powers and was thus sold by her parents to the monastery. She was subjected to experimental merging of a human and a katawara, and fused with Kagan, a golem katawara. However, the process went haywire and she lost control and any physical traces of her humanity, escaping and killing many people while in a daze, including her family. After she managed to recover, she was now Shakugan.