Well, since WoW said it, I'll explain why I don't think Soriku is Mafia. Last time, as everyone knows, Gnizmo added incorrectly That Guy as Mafia (it unbalanced the game). I knew there was something suspicious, as Gniz mentioned that he "couldn't say how many mafia were there". Most people would think that adding a last-min entrance would side him as townie, but I figured out that Gniz had indeed decided in the moment the role of That Guy. So, I attributed that to Gnizmo's (and VGC in general) inexpertise, he didn't know that a 9 player with 3 mafia would be difficult, and that's why I thought there was a possibilty of him being mafia. In other words, I didn't take for granted what WoW indeed did
This time, though, we fought hard before the start to make the game balanced. WoW repeated time and again of the 3 townies per mafia rule as a golden rule. Before, we were 13. So, it's safe to assume 3 mafia (and maybe a traitor sided with them). Now, we're 14. The rule still gives 3 mafia, 4 would make it horribly unbalanced again. And I really doubt Jo would do that, specially after the insistence. And I really doubt that if there wasn't a traitor before, it'd be introduced now (it's possible, but unlikely). We also can discount Soriku being a serial killer or a serial killer preventer, since it'd make no sense.
So, that concludes my line of thought
On an unrelated note, what does FoS mean? I can imagine what it means, but what does it exactly mean? Field of Sight?
This is what happens when I take too much time to post