The sub is out now.
Okay, so I can safely say that I guessed Rika was Oyashiro-sama in the first arc. I mean, there a fair amount of hints...
Spoiler for everything:
1. Opening song, takes of KITSUNE mask, don;t need to elaborate as I've balthered about this too often.
2. Her being the most "innocent".
3. Her exclaiming the word "Mi" may be just a cute thing, but doesn't it also mean demon?
4. Her trying to stop The Demon in Watanagashi-hen "I'll have a word with older sister cat" could be looked at like this: Two powerful entities exist in Hinamizawa, The Demon and Oyashiro. Oyashiro could be in Rika, and the demon in Mion. Now, ONLY in Wata-hen does the demon manifest itself in Mion cuz of the weird incident. Now, Oyashiro may not like this demon too much, which is why she/he said what she/he said to K1. For once, K1 didn;t really incur the wrath of Oyashiro in that arc. He did pretyy much piss of the demon in every way.
5. Rika being punished in the flashback. If Rika is the manifestation of Oyashiro, she would hold a grudge against Satako for what she did to her back then.
6. The "Preview" voice may have a connection to Oyashiro.