YuYu Hakusho, Volume 8 (YuYu Hakusho #65-73)

The Blood-Slaver NodesDr. Ichigaki's ultimate biological weapons are in the ring, but Team Urameshi is suddenly having a severe attack of conscience. After Kuwabara's enlightening reverie about how Dr. Ichigaki implanted blood-slaver nodes in the brains of Master Mitamura's martial-arts students, Yusuke and company just don't have the heart to conduct their demon-slaying business as usual. Meanwhile, the Shadow Channelers - the ninjas of the Demon Plane - are on deck. With their fiendish adrenalin pumped up to the max, Team Urameshi better pray that Yukina the Ice Maiden, who came to watch, turns out to be their lucky charm.