So anyway, I was looking at Chapter 411 with the letter from Shou Hei Kun with the broken seal. Now I think this is the same letter that Shin is referring to in Chapter 418. Now if that is true, Sho Hei Kun is working somewhat as a double agent as he just passed important information to the Hi Shin Unit. I have felt for a long time, since he helped Sei with the planning for the Battle of Sai, that Shou Hei Kun has been distancing himself from Ryo Fui.
Now, the fact that the seal was broken I think indicates that one of Ryo Fui's minions intercepted it, as he doesn't fully trust Shou Hei Kun since the Coalition Arc. Obviously it was in code and talking about battles etc, so Sho Hei Kun could easily pass it off as just advice to one of his students.
Now the fact that Shou Hei Kun knew about Ai's strategy, would suggest that Ryo Fui also knows about Ai's strategy and is indeed involved in it. Ryo Fui indicated so much in his monologue at the end of chapter 418. Han O Ki's son indicated that the gates wouldn't fall easily, however, it falled moments later, which Han O Ki expected. This would suggest that Han O Ki and Ryo Fui are working together on some level
I just created this as a blog post to whore the achievement.;)