I'm still at a loss for words as to who the traitor is. Shinobu seems like a red herring. Is it one of the Akazaya 9?
We can obviously rule out Kinemon, Kawamatsu, and Ashura Doji. Plus, Inu/Neko/Raizo because they all suffered at the hands of the traitor. That leaves Kiku, Denjiro and Kanjuro. I think Denjiro is clearly Kyoshiro, adopting a fake identity like Ashura/Shutenmaru, because a Samurai subordinate as strong as Kyoshiro doesn't appear out of nowhere without a Top Tier leader. He's the equivalent of a Yonko Commander without a Yonko level leader? Bullshit. Plus he's a money changer which is a dead giveaway. However, he is clearly Oden-allied and on Hiyori's side. When Orochi goes to Onigashima he's in charge of overseeing the Samurai prisoners, and he'll let them all free. It makes no sense as to why he'd be a traitor 20 years ago. Plus Denjiro would have no idea what the time travel crew is doing.
That leaves Kiku and Kanjuro. Both time travellers. I can't rule these two out. I'm afraid they'd both be super fucking random though.