I think so too. There's no way Shibe would turn against him without any good reason, after all what they have been through
It totally has to be an act. Yuuichi's expression looked the same as during one of the last times when he was also acting like he was losing... And the fact that they showed how Shibe had been close to that guy since the beginning, even makes me think that Yuuichi made him become close to him in first place exactly fór that reason.
I'm just curious why the other smart (short) guy seems not to be planning something, I expected more from him...
I had feeling Ryuusei is no good, and I also knew that Keiko had the key. Now it's just a matter of how to expose these two. I do wanna know why Shibe turned against Yuuichi, but I have a feeling this might be an act so fingers crossed.