Kimetsu no Yaiba season 2 ended with a rain of compliments on both the script and animation from audiences around the world. In episode 11, the drama creates deep moments with sad memories of the human past of two legendary brothers Gyutaro and Daki. Besides, the scene of Tengen Uzui’s last life with three wives is also especially loved by many viewers because of its charming humor. However, the most outstanding highlight in the final episode of season 2 is the fact that Nezuko’s demonic blood saved the lives of Inosuke, Tanjiro and Tengen Uzui at the last minute, and Tanjiro also revealed that this demonic blood has the ability to burn Devil’s toxins in the body. This caused many viewers to question whether Nezuko’s demonic blood can cure the disease that Princess Kagaya Ubuyashiki – the leader of the Demon Slayer Corps, is suffering from?
Unfortunately, the answer here is not possible. To understand why this is so, it is necessary to go back to the source of the illness of Princess Kagaya Ubuyashiki.
Unlike the case of Inosuke, Tanjiro or Tengen Uzui – who were poisoned during the battle with the upper mystical continent, Princess Kagaya Ubuyashiki became ill due to a curse that fell on his family. This curse is deeply related to the demon lord Muzan.
Hundreds of years ago, when Muzan Kibutsuji became a demon lord, his clan, the Ubuyashiki clan, suffered a terrible curse to pay for the birth of an evil demon. Since then, the children of the Ubuyashiki family all died prematurely at birth, until a shaman appeared and showed him how to ease the curse. Generations of the Ubuyashiki family would have to marry women designated by the shrine so that their children would not be born prematurely. However, these children are also very fragile, when young, boys will look like girls and as they grow up, they will start to have scars that spread all over their bodies. The Ubuyashiki family cannot live past the age of 30. To remove the curse, they must destroy Muzan Kibutsuji. Therefore, generations of the Ubuyashiki family built and led the Demon Slayer to hunt down Muzan Kibutsuji.
Princess Kagaya Ubuyashiki is the 97th leader of the Demon Slayer Corps. He also did not escape the curse of the clan. Kagaya inherited the clan at the age of four and married a shrine maiden at the age of 13. Starting from this moment, Kagaya’s face began to appear scarred that looked similar to the symptoms of Inosuke, Tanjiro’s poisoning and the yin pillar. At the time Tanjiro joined the Demon Slayer, Kagaya was about 24-25 years old, the scar spread across most of his body, his eyes were blind, he moved completely with the help of his wife and children. It can be said that Kagaya is in a critical stage and his life time is short.
Since Princess Kagaya Ubuyashiki was not sick from common demon poisoning, Nezuko’s blood demonic magic was useless in curing him.