I don't view his wish granting as sadistic personally. Perhaps because of his new position and uncanny ability to see into a person's heart and know the desires behind their actions, their Wishes; he simply acts upon those desires, in a sense forcing the person to realize they're there. Usually, when he grants the wishes of the Seals or Angels its during their fighting over the state of the Kekkai's of Tokyo, so it can look somewhat sadistic.
It's unfounded, but I have a feeling that Fuuma's wish involves his dying at Kamui's hand instead of the other way around, something that won't happen unless Kamui realizes his actual wish instead of the one he's clung to for the majority of the manga. Whether Kamui's wish will actually counter the fatal nature of Fuuma's I don't know or not, no one but Fuuma seems to actually know Kamui's actual wish. Perhaps Kamui's wish will work in together with Fuuma's own which will resolve matters and possibly win the war for humanity. Because I don't really believe that Fuuma himself believes Humanity should perish. If he did I think, he wouldn't be helping show the flaws in their behavior to the Dragons of Heaven and actually helping them understand themselves.
He aids Yuza in regaining Inuki by putting her into a position of danger and desire to be capable of aiding her friend and comrade, which ended up in the recreation of Inuki to prevent Fuuma from harming Kamui further during that time. As Fuuma tells her after Inuki's appearance that her 'wish' to not die must have been genuine and true before departing the scene.
Likewise during his encounter with Nataku in X18, he notes Nataku's change of heart and thus the changing of his ultimate desire or wish. When Nataku firmly decides to act on that wish, Fuuma states he'll grant it for him. Unfortunately, that wish results in Nataku's death much to Karen's horror. He tries to explain that some people's wishes may make others suffer, but one should respect them regardless. Also he questions her views on harming others, making her actually reflect on his words and actions and she later realizes that perhaps sometimes a person can end up hurting someone they don't mean to hurt without even realizing it.
This I think might play an important part in the dynamic between Kamui and Fuuma, that Kamui's current false wish will end up hurting them both in the end. Also Fuuma states he'll grant Kakyou's wish, but despite Kakyou once at the beginning stating that wish was to die, Fuuma's never once actually stated he'll kill him to grant that wish. So I think that perhaps Fuuma has seen something in Kakyou besides a death wish.
I don't think he can not not see the desires or wishes of those he meets, which might actually cause someone to realize that some people are uncaring, petty, or don't really care if they live or die. This may be why he doesn't seem to care over much over the loss of life involved in his destruction of the Kekkai. If they don't care much for their life or the world and people around them, why should he care for their lives?
Which perhaps is why he purposely sent that one little girl out of the area of the Ebisu Kekkai once so that she or her mother wouldn't die in its destruction, because she genuinely wanted to live no matter what. He states after he destroys Ebsiu that finding people who don't want to die no matter what is rare in Tokyo.
I hope I understood what you wanted and answered it properly, let me know if I misunderstood though.. o7
Interpretation
It's unfounded, but I have a feeling that Fuuma's wish involves his dying at Kamui's hand instead of the other way around, something that won't happen unless Kamui realizes his actual wish instead of the one he's clung to for the majority of the manga. Whether Kamui's wish will actually counter the fatal nature of Fuuma's I don't know or not, no one but Fuuma seems to actually know Kamui's actual wish. Perhaps Kamui's wish will work in together with Fuuma's own which will resolve matters and possibly win the war for humanity. Because I don't really believe that Fuuma himself believes Humanity should perish. If he did I think, he wouldn't be helping show the flaws in their behavior to the Dragons of Heaven and actually helping them understand themselves.
He aids Yuza in regaining Inuki by putting her into a position of danger and desire to be capable of aiding her friend and comrade, which ended up in the recreation of Inuki to prevent Fuuma from harming Kamui further during that time. As Fuuma tells her after Inuki's appearance that her 'wish' to not die must have been genuine and true before departing the scene.
Likewise during his encounter with Nataku in X18, he notes Nataku's change of heart and thus the changing of his ultimate desire or wish. When Nataku firmly decides to act on that wish, Fuuma states he'll grant it for him. Unfortunately, that wish results in Nataku's death much to Karen's horror. He tries to explain that some people's wishes may make others suffer, but one should respect them regardless. Also he questions her views on harming others, making her actually reflect on his words and actions and she later realizes that perhaps sometimes a person can end up hurting someone they don't mean to hurt without even realizing it.
This I think might play an important part in the dynamic between Kamui and Fuuma, that Kamui's current false wish will end up hurting them both in the end. Also Fuuma states he'll grant Kakyou's wish, but despite Kakyou once at the beginning stating that wish was to die, Fuuma's never once actually stated he'll kill him to grant that wish. So I think that perhaps Fuuma has seen something in Kakyou besides a death wish.
I don't think he can not not see the desires or wishes of those he meets, which might actually cause someone to realize that some people are uncaring, petty, or don't really care if they live or die. This may be why he doesn't seem to care over much over the loss of life involved in his destruction of the Kekkai. If they don't care much for their life or the world and people around them, why should he care for their lives?
Which perhaps is why he purposely sent that one little girl out of the area of the Ebisu Kekkai once so that she or her mother wouldn't die in its destruction, because she genuinely wanted to live no matter what. He states after he destroys Ebsiu that finding people who don't want to die no matter what is rare in Tokyo.
I hope I understood what you wanted and answered it properly, let me know if I misunderstood though.. o7