No Misery was one of the main characters in Ghost Blade and was set to be one of the strongest existences in the entire series. But even with his great power, he still chose to become a human. There could be many explanations for why Wutian chose to become a human voluntarily. He might have thought that becoming human would help him achieve his goals. He may have a special affection for humans or he may think that he can better understand and control his own power by becoming human. Wutian might also think that he was a kind existence. He did not treat humans cruelly. On the contrary, he hoped to help humans become stronger. He believed that becoming a human would give him more freedom and power to better achieve his goals. It was also possible that Wucai had volunteered to become a human because he believed that he had the ability to help humans get rid of the threat of ghosts and become a part of the human race, contributing to the peaceful development of mankind. The above are just some possible explanations. The specific reasons may vary according to the needs of the plot.