The unnamed shinkitsune was Kuyomaro's twin brother and the creator of the sword Kyoseiga. He forged Kyoseiga from his own fang. He was also the one responsible of Kuyomaro's initial defeat, destroying Kuyomaro's body, but getting killed in the final attack himself. He was a powerful shinyōkai, as even Kuyomaro himself regarded him as his equal. According to Kuyomaro, his shinyōki was "painfully pure" and was thus the only known yōkai to be able to resist and even completely block the effects of Kuyomaro's evil shinyōki.
Not much is known of this enigmatic figure, other than that over a thousand years in the past he forged a powerful sword of his fang and named it Kyoseiga (巨精牙, Great Spirit Fang). In the same time, his twin brother, Kuyomaro, became increasingly power-hungry, causing more and more chaos and destruction. Finally the brother couldn't look away from his brother's evilnessany longer, and confronted him. The battle raged for a long time, and the two brothers seemed equal. In the end, the noble shinkitsune realized he had no other possibilit but to take out Kuyomaro with him. He left the Kyoseiga for his descentants to take care of and charged up one final attack. However, Kuyomaro managed to partially escape the attack, leaving his body completely destroyed. The unnamed shinkitsune then died of the energy loss of his final attack, bidding his farewell to his family.
The unnamed shinkitsune's legacy continues to live on in Kyoseiga, that has now ended up in the possession of Gingichi Tsukihoshi. Kuyomaro, having realized the power that the sword holds, now seeks to obtain it himself.