No doubt Takashi became the new Kurusu, or more like he already was. The Naked Emperor already said that "You are Kurusu as well", so it seems they refer to every evolved human as Kurusu (Den of Madness). It looks like in exchange for becoming considerably stronger and sturdy they loose all their emotions, as you could see by Kurusu (the original one) questioning Tomabecchi about what it means "to like someone". Kurusu killing Takeshi's love probably triggered his awakening, he seemed to go totally mad (and his hair went up lol) when he saw the severed head. Before he still had normal human emotions in him, like when the school building reminded him of the time he was bullied or when he thought of the girl, but on the last page it looks like he really became the new Kurusu, totally void of emotions.
@Matt I think the same. Like the Naked Emperor said, he kills everyone who seems to be above him in social standing, so he probably went through the school to look for such guys/girls - the ones he slaughters at the place the group was at.
Besides all that analyzing, great volume! I am a Hero never fails to deliver, the revelation of the evolved humans was a really good move. How the three fought was so weird and creepy. Now I wonder what Takashi, the new Kurusu, actually wants. The Naked Emperor only wanted to destroy the ones above him in standing, while the old Kurusu obviously just wanted entertainment, mainly through fights. Seeing how Takashi/Kurusu wants to head to Tokyo he must have some kind of specific goal there.
Oh, I really want the next volume now!