Group Dynamics: Pyramid +1
First for those of you who have not familiar with Weiss (hello, Swift), let me sum up Weiss canon, and Omi's part in it, as neatly as I can.
Once upon a time there was a cute puppy. It was kind of an ugly puppy, but cute. Think Shar-Pei. The puppy had a family. They were kind of crazy, but they gave him bones and cuddles and earscritches, and the puppy was very happy.
One day, the family left the cute puppy on the side of the road, and someone picked the puppy up and trained it to be an attack dog. The dog grew out of its ugliness, but still kind of looked like a puppy. Think Golden Retriever this time. He got sharp words and training, and the occasional earscritch and treat.
And-- like in Dickens, or really bad anime-- it turned out the person who picked the puppy up happened to be related to the family that left the cute puppy on the side of the road in the first place, and so the puppy ended up ripping out the throats of the family it once had. (And the puppy got hardly any earscritching.) I seriously spend most of the first Weiss series yelling 'for God's sake, someone give him a hug!' at the screen. (And almost no one does. I think the only real hug he gets is from Manx.)
The point of this is not so much to say that my canon hurts, but to say that Omi, to put it bluntly, is generally happy with whatever scraps of affection he gets. He is painfully grateful in canon when Aya tells him "you are not Takatori Mamoru, you are Tsukiyono Omi."
This is reason #1 why the Pyramid works: because Omi has so little love, for so long, a little real love goes a long way.
Reason #2 is Swift.
I've put off talking about Swift for a really long fucking time. Because I'm paranoid, basically, and Swift was really good for Omi. Is really good for Omi. And every time I think something's stable with Omi's relationships it goes to hell in a hurry. So. Um. Yeah. But what the hell, I like to talk.
I hadn't read the second Wraeththu book-- Swift's book-- when I saw his application. And I remember I voted in thinking "Oh, man, Swift will never knew what hit him." Because there were so many things about Swift that just clicked with Omi's personality, and then Swift arrived in camp, and it was even better-- or worse-- than I had thought.
Omi was immediately drawn to Swift, and fell hard and fast-- knowing Swift was inherently slutty Wraeththu, knowing Swift was essentially married and had a son, knowing this was untenable and temporary. In some of their earlier 'getting to know you' threads, you'll notice Omi asking Swift a lot of questions about his home and family-- and some of it is genuine curiosity. But some of it is Omi trying to remind himself; this won't last. You've just done this. Don't do it again.
And it didn't help. At all. One bit. Omi. Just. Fell.
Swift has Ken's openness and genuine empathy, and desire to make things better; and Omi's pretty much helpless against those traits. And Swift is strong; he won't fall apart if Omi does. He's one of the few people who can just genuinely make things better for Omi, just by being there. He's got a tremendous generosity of spirit-- he's probably one of the most generous people Omi knows-- and that moves Omi very deeply.
And so their relationship progressed and Omi realized it didn't matter to him where Swift slept or whatever the hell he did when he wasn't around Omi; the affection and caring he gave Omi were just...enough. And so sharing wasn't as weird to Omi as it might have been under other circumstances.
And reason #3 is that Ken is deeply fucked up. Omi is just not enough to keep Ken sane, and Omi's all too aware of it. In canon, Omi eventually lets Ken go, I think for his own sanity as much as out of concern for Ken. Ken's deepest confessions about his insanity are made to Aya, not Omi, and again, I think that's out of concern for Omi. I just don't think Omi can handle Ken's level of crazy on his own; his own sanity is too fragile.
Reason #4, tied to #3, is that Francescu is awesome. The first time Francescu really hit Omi's radar was by caring for Ken, and you can't make a much better first impression than that. I think Francescu really fills the last need Omi has; that for family. He basically decides his family comes ahead of Weiss by the end, and I think it's his longing for what he only vaguely remembers that compels him. The one flashback we get of Omi is only vaguely of his mother, and not of his father at all; the strongest memories are of his two older brothers. I don't think it's a coincidence that Francescu is an older brother.
So Omi is happy with scraps, and with his life the way it's arranged now-- and Omi is very much an arranger-- he has a good deal more than that; the family and friendship he needs, and unlimited kisses from two hot guys he adores. You really can't ask for much more.