Arashi announces that she is now a Dragon of Earth. Both Yuzuriha and Sorata are shocked by this declaration, but when they try to press her for more information, she remains silent.
Aoki says that he thinks that it was to protect Sorata and, sure enough, that turns out to be the case. In her mind, killing Kamui will end the fight and will keep Sorata from sacrificing himself for her sake. OK, I kind of get the logic here, but wouldn't killing Fuma accomplish the same goal? She could have faked her defection using that as a cover story and then ambushed him when his guard was down. It would have been an interesting strategy, but it isn't the case.
As both Yuzuriha and Aoki are too injured to fight and Subaru is still catatonic, the task of saving the world falls on Kamui's and Sorata's shoulders. I was thrown when Kamui said that they couldn't use their powers anymore, but I prefer to go with my explanation that they were just in no shape to fight.
While Kamui still hasn't awakened yet, he takes the divine sword and goes to confront Fuma. Not surprisingly, he sicks Arashi on him. It isn't really much of a fight as Kamui doesn't want to fight his friend and tries to reason with her to no avail. I can't fault him for the effort really, but it does force Sorata to step in and save Kamui, even if it means taking out Arashi.
It turns out that neither one can bring themselves to hurt the other. Fuma doesn't take kindly to the "betrayal" and threatens Arashi. She doesn't seem to make any effort to fight him. She just sits there. She may not be able to take him on her own, but she has back up. You could have at least tried something.
Before Fuma can deliver the killing strike, Sorata leaps in front of her and takes the impaling in her stead. He could have just hit Fuma with his force lightning and saved her, but this is more dramatic and it fulfills the prophecy that he would sacrifice himself for the woman he loves.
It's a fairly poignant scene as Arashi weeps over her dying love. You kind of wish these two got to spend more time together. Sorata doesn't go down without a fight as he uses the sword as a conduit to severely wound Fuma with his electricity. It was nice to see Fuma not only get caught off guard but actually take a hit and get wounded. The fact that he survived is no surprise, but that was a given seeing as there's still another episode left and Fuma is Kamui's to deal with.
There's only one episode left and things really are looking grim for the Dragons of Heaven. At this point, they may need a hand of God or an army of archangels to turn the tide. We'll have to see how things play out in the last 20 minutes of the series.