Neuro's hair changed.... But that's about the only thing I noticed! I remember in a previous chapter (during the fight against Tiara, I think?) he said the triangles he wore in his hair were little capsules of demonic power.
So, they disappeared after losing so much power summoning a 7 Weapons of the Demon Court... Maybe it's also got something to dow with the fact Neuro said he was becoming more human as he spent more time on Earth? >>