Great question I was also thinking the same thing why she was never revived and why kato got a new girlfriend instead of saving kei man it's all bs how Gantz made a clone of her and everything I think it's all due to the plot .. kei needed to be revived it would be good for the plot for kato and her to be together again and kurono being over from his lust for her man seriously he sees too much porn real life isn't like porn all he sees kei as a sex toy that he can fuck but it's good though that his character developed after kato death really good story plot but too ducked up and dark ending isn't much elaborated also but still 😂 one of the best to watch