Adisa N.

I don't know, but I guess Renya Karasuma (he's in 30th tankoubon) is the leader of the syndicate. I suspect him since I read "Nanatsu no Ko"'s lyrics. The last line of the lyric is something like this : "Go to its old home at the mountain.." we know that Renya Karasuma's home is old, and it situated on a mountain. Maybe it's a pretty big hint Gosho has given to us, I don't know.. Second, I guess the true name of the organization is something related with crows, considering the members are dressing in black, just like a crow's feather, and they use a song about a crying crow as the boss' email. Renya Karasuma has KARASU (crow) on his name, which leads to the theory of the true name of the Syndicate is tied to the leader's identity. The last, Renya had a fetish to Crows (Karasu), which explains why BO members are all dressed in black. But it's just me though.