wait what?? i cant seem to make heads or tails of this manga. =/ so is the glasses wearing...

its his cousin

so the long white haired guy is the cousin??

Mi Sheng, glasses wearing cousin, made a deal with a shadow-like entity in return for having xiaoWei. However, the deal has changed Mi Sheng physically into that blood person who keeps attacking xiaoWei's new friends, Feng Ming, Richard, and Shaurice.

I'm guessing...considering the 'Sherlock Holmes' vibes that it's Moriarty.

Anyways, several chapters back (Falling Apart arc?), blondie attacked Feng Ming and xiaoWei hurt blondie very badly and Xiao, xiaoWei's twin brother (older?) and Feng Ming's ex lover who used to be part of their group, took blondie away.

It's just in the past couple of chapters (Fairy Tales arc) we realize that blondie is actually Mi Sheng and Xiao just informed xiaoWei that he became this way through a deal. He never said with whom or what the deal consisted of.

Does that help you?

I meant blond person not blood person. Damnit, I need an edit ability on my posts.

ah thank you! yeah that helped me a bit. i wish the story would be more clear on what is happening so parts like this wont confuse me so much.