Now that I've had a chance to process, I'm going to vent at Rin a bit. Yes, Rin, who has fuck all to do with Yukio's insane actions, but I'm mad at how he indirectly caused Yukio to blow up at Shiemi. As someone who has dealt with an emotionally distressed sibling, this is exactly why you never let it go this far. Rin avoiding Yukio caused the burden of confronting Yukio to fall on Shiemi's shoulders, and she ended up getting the brunt of Yukio's rage. While Yukio is out of control and bears the most responsibility of his actions, it is Rin's, not Shiemi's, responsibility to deal with his sib, and that includes enduring the rage. Goddammit Rin.
I think it's way early to blame Rin for this Shiemi and Yukio scene without knowing why she's talking to him or what she said. Let's not forget: Shiemi is keeping secrets too, and we've already seen one change in her behavior towards Yukio (when she yelled and insisted he come to the Christmas party). Maybe she knows something about him we don't?
But with Rin, we actually haven't gotten a look into his thoughts or feelings in a long time now. He's tried reaching out to Yukio, dozens of times times throughout the series, and even outright calling him out for never telling him anything. But Rin also has no idea the weight of what Yukio is dealing with. It's only recently that it's become obvious to those around him that something is seriously wrong, because up until recently, Yukio hasn't outwardly been very different than usual.
But not only that: there have been little hints here and there that a change occurred between Rin and Yukio after Aomori. We've been seeing how everything up until now has impacted Yukio, but very little about Rin -- which I think is supposed to be intentional. He may not be as complex as Yukio is right now, but everything going on around them has to be having an impact on him too.