Yuiichi the main character , assuming he have the plot armor , thus he can't be the traitor
Tenji the first traitor , but turned heel and assuming this is correct , then he can't be the traitor
Sawaragi the first mole , assuming she stated the correct thing in the reveal chapter , then she can't be the traitor
Kokorogi the confirmed traitor ... but there's no clear explanation what the motive is
and thus Shibe currently have the greatest chance to be the traitor , but there's no clear explanation