Ok, my guess was correct again, Idk why I found Shibe so suspicious a whole time in this game, especially the moment when Shibe try to stop Shiho when she wanted to do something about her plan.
Ok with this, all become make sense now. When Yuichi got catch by zombies, those are not a real zombie, a fake zombies yeah, and that's a part of his plan and also Tenji. Finally we can see the Yuichi's epic moment!!! Been waiting for this.
Yuichi knows it, he did all of this with intention. And for the second traitor it's so hard to guess, but Yuichi has a possibility tho... But I feel like Shibe is the second traitor. The moment Kokorogi was attacking Shibe maybe because she knows Shiho is there, and she is trying to lure Shiho out.