I realized I haven't commented on this yet (I only ranted on plurk lol)

RIN LOVES ARITHMANCY. It's his favorite and best subject, his only refuge from History of Magic, the only thing in his life that seems to have logic and make sense. I'm gonna reply to the post soon.

I think Sano might have taken it as an elective as well, but probably not with Akatsuki.

As for Yogi... Not a chance in hell. I think Akatsuki might freak him o ut similarly as Akari-sensei does. I am canon blind though, so be gentle on me. ^^