I don't think we ever saw Schera in Cold Steel 3 so I just assumed it was something that happened off-screen at some point over the past several years. As for Mueller/Julia, I remember this at least being hinted at in Sky, particularly somewhere in The 3rd. (I think it was implying that it could become a thing in the future--not that that it was already a thing that was happening) ---
I didn't do guru this year but azuarc can be in my sig anyways.