This fight is just building up to the climax, Yukio seems quite docile, like not trying to fight back in any case, just taking all the punches. Demon!Rin no longer has distinctive speech pattern so I take that some kind of 'integration' is happening with his bipolarity. I am not sure but
this is what I feel with Rin now, some kind of 'spiritual/demonic' mental disorder.
But what really is reinforced is Rin's belief in taking Yukio as a wimp. Will he really say this to any of his human/lesser powerful friends? For most part when a protagonist is being built, he is mostly reactive but here for the first time I feel Rin is driving the narrative, pushing his 'politically incorrect' diatribe in boldface while changing from protector to Yukio's abuser. And Satan is enjoying Yukio as a punching bag, egging Rin's anger. And Yukio for all the protection has scratches on his face from broken glass. Perhaps Satan has to be willful in protecting Yukio? Not all injuries can be shielded or taken care of, perhaps what keeps him alive is more important for Satan.
Shima is given the task to pull Yukio out of the fight, so I wonder if he will give the escape route for Illuminati after Lightning arrives. Considering Koneko is still with the sword, it will be used sometime during this fight, to focus Rin's power as he has relatively weaker control with size and intensity. Anyways, Rin is looking increasingly like young Satan did, kind of understand why Satan thought he took after him and markedly different from when he is in control of himself.
A little note, about Yukio's eyes, they look like a few people I had known just before they finally took their leave, did the deed and all. So he is indeed very suicidal and kudos to Ms.Katoh for bringing that look out. Calling for help is so passe, he just wants it done pronto, I truly believe he would be very thankful to Rin for it. Even if he says it for the world and all, it is very selfish.
Rin is good at provoking Yukio's anger though, until he prodded, Satan was just watching, the moment he talked about Yukio not wanting to be looked down upon, Satan got strong enough to retaliate. Both Rin and Yukio don't take well to being challanged, anger is first reaction. Rin loses to his demonic urge, Yukio has Satan take over. A little note from before about Yukio's anger was that it is more dangerous than Rin's. Mephisto had Shima face him during those times and I really want to know if Shima came to uncover Yukio's Satan eye during such times.
I remember, that Yukio had frequent blank spells, gaps in his memory, I wonder if he is in control of himself during such times. Last chapter also had his memory flashback in which he was remembering the damage to ship and murder spree he did as Satan's power got away I guess. He is obviously worried of uncertainty and feeling of losing control over himself when the price is similar to Blue Night maybe worse and Mephisto has no calculation of this time-space.
Thanks to @chinonamida for English translation, it really changes a lot of comprehension. I appreciate your and other contributors' early translated panels for the manga, still prefer them over the regular version. To add, the theories over the running period of the comics are also very insightful.
