This is purely theoretical seeing as we’re not even sure that the person who tried to kill Soma is Ciel’s twin but, assuming it is in fact the Twin and that he’s after revenge against his own brother for what happened four years ago, I’m wondering if Yana’s purpose in having the twins confronting each other precisely in this arc isn’t because it’s finally time for our!Ciel to reflect on himself and several choices that he made ever since their parents’ death.
What I mean by that is that if Soma’s shooter is in fact the Twin…
…then you can feel his dead cold anger and vengeful intent through the violence of the attack against both Soma and Agni. Even if Agni was ultimately killed by the other man, if the Twin is Lord Sirius then Lord Polaris, as his butler and Agni’s killer, is obeying him anyway, so if ch126/127 were all about the Twin’s revenge, then you can just see how angry he is at his brother, which is why Agni was killed so violently.
And that’s precisely where the Twin could be different from our!Ciel, if that’s indeed him.
After all, we don’t know exactly what the Twin’s existence could have been like during these last 4 years and we don’t even know what he currently is (BD-like? still alive?), but what’s certain is that he wasn’t surrounded by what was left of his family all this time, unlike our!Ciel.
And that’s the thing, our!Ciel pretends that he only cares about revenge, that it’s the only reason he is still alive and I don’t doubt that he actually really believes it deep inside, but at the same time, Soma is right when he says…
…that Ciel is aware of the love around him, but that he refuses to accept it.
However, if the shooter of ch126/127 is Ciel’s Twin, then he wasn’t as lucky as Ciel during the last 4 years: from being sacrificed to being… revived/cared after by the blue sect, he didn’t get to be looked after by Lizzie, he didn’t get to meet the same people as his brother who cared about our!Ciel even if he always pushed them away… So maybe that’s why his vengeful and murderous intent is greater than our!Ciel at this moment.
Because sure, our!Ciel believes he only lives for his revenge and he pushes people away because he’s indeed terrified of being happy, but at least he knows that he has people caring about him, which is not his twin’s case at all.
So if the two brothers indeed face each other in this arc, I’m thinking it might make Ciel realize that Soma is right when he says that Ciel only keeps trying to be alone with his revenge, but he definitely can’t manage to be doing that as well as his brother, since his brother truly has no one at all to divert his mind from revenge.
You could say that it’s as if Ciel’s twin would be revenge personified, because that’s truly all that he really cares about, whereas our!Ciel, despite inwardly believing that he only cares about revenge, might be lying to himself because “the love around him” ended up having an effect on him after all.
So facing his twin might be what will trigger more development for Ciel, because it might force him to realize that if he truly was only living for revenge (without a care of anything besides that), then he would be a lot more like how his brother currently acts.
Not to confound, I don’t think Ciel will ever stop wishing for revenge, but reflecting back on all the choices that he made ever since his parents’ death is an important part of his character development, and maybe facing his twin is the only way to trigger that (besides the involvement of Soma and possibly Lizzie in his everyday life).
Finally, if the twin really is all about revenge (as I believe he could be) then…
…Lizzie is probably used (or going to be used) as a way to hurt our!Ciel as well, just like it was supposed to go with Soma and Agni. Maybe the twin intends on making Ciel experience what it feels like to really be alone, like himself was ever since he was sacrificed on the altar, while Ciel managed to escape and stole his identity.
Obviously though, Lizzie probably doesn’t know about that part (and about Soma and Agni being attacked) and she stays with the twin because she’s confused about his revival (?) and pained at the thought of our!Ciel lying for the last 4 years. However, there is a strong possibility that the twin doesn’t care at all and she’s nothing but a pawn in order to get to our!Ciel and hurt him.
TL;DR character development and self reflection for our!Ciel is probably a sure thing in case the one who almost shot Soma is indeed his twin and he’s looking for revenge against our!Ciel for everything that happened 4 years ago.
Everybody’s fixated on the fact that I stabbed my brothers in the back, that I betrayed my brothers. And maybe to Roman Reigns and Dean Ambrose we were brothers. But to me, they were just business partners. For two years, every night I came out here and I put my fist out and I said believe in The Shield. And every night what I meant is what I’m going to tell you right now. It’s that you and everybody else better start believing in Seth Rollins - 2nd June, 2014. The Shield implodes