In the shadows waits for an evil creature wanting to devour human flesh. Without it, the demon will become weak, which is extremely dangerous in their world. Tanjiro Kamado thought this was the fate his sister would have after being infected by a monster, except her transformation was a little different.
After grabbing his sister Nezuko, Tanjiro raced to the village to get his sister's help. It's at this moment when Nezuko attacked Tanjiro, at that moment that a demon slayer appears, Giyu Tomioka. He tries to kill Nezuko, claiming no chance for her, but something strange happens. Nezuko defends her brother; it is clear that Nezuko and her demon half were battling. One craving the flesh of those around her, the other wants to protect her older brother. This is just the first of many differences Nezuko has with other demons.
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During his journey to save his sister, Tanjiro travels to Sakonji Urokodaki, a retired demon slayer, to train. During those two years, Nezuko slept, never waking. This is extremely strange because demons don't do that. Urokodaki theorizes that perhaps instead of eating humans, Nezuko is attempting to gain energy by sleeping. This means Nezuko can help Tanjiro on his missions, but when she does need to regain her strength, she'll sleep for extended periods, making her vulnerable.
Another thing that makes Nezuko stand out is her fighting ability. As a young demon Nezuko is powerful and learns fast. She shows this when fighting against Susamaru. The two battle it out, kicking Susamaru's ball back and forth at first, Nezuko's food is blown off, but after regenerating, she can keep up with Susamaru. Even nearly hitting her in the head with the ball.
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