What Squalo had long come to understand of his Boss was several things. Squalo was by no means a slow leaner (he could see someone through in a heartbeat, strip them down to their bare bones in one glance, see every tick, every quirk, within a few minutes of meeting them; it was a trait that might have become annoying to anyone else that possessed it, but Squalo, unlike most people, did not react to the idiosyncrasies because he didn't care about other people), so once he had gotten past XANXUS's blinding brilliance, the idiosyncrasies began to show up. And, as usual, once Squalo knew something, it never left his brain- it was carefully compartmentalized for later use. So it was eternally surprising to Squalo how XANXUS seemed to be able to continuously startle, irritate, and catch him unawares, despite the fact that Squalo already knew these things, and had, indeed, known them for a long, long time.
The first thing was that XANXUS was, in the end, like a large, predatory animal. A cat, in fact. This, being the primary topic of information on XANXUS (the thought had struck Squalo when he was fourteen, XANXUS sixteen, and XANXUS, in the middle of class, had opened his mouth widely and given a cavernous yawn before sprawling his lanky limbs around his desk in order to make himself more comfortable for a nap; as he had done this, Squalo had realized, and was left dumbstruck for several seconds), several other things had filled out as subcategories shortly thereafter.
First, that because of XANXUS's inherent nature, XAXNUS liked all things that agreed with him in excess. For example, he slept quite a bit- though he went to bed late, he was almost never seen out of bed before noon (on good days; if he had a hangover, all bets were off until at least three in the afternoon), and he took naps wherever he could. Squalo had walked into a room several times where he had known his Boss to be, speaking to what he presumed to be an alert, interested party, only to be responded with a resounding growl and the nearest handy projectile hurled at his head, or, alternatively, complete silence, broken by soft breathing.
Another thing XANXUS liked, perhaps to no great surprise, though at times to Squalo's dismay, was sex. XANXUS, being not only predatory but arrogant, had no trouble in finding it, either; wherever they went, XANXUS seemed to pick some up, though he never chased ass. In fact, it was usually a quick fuck and then a farewell, and on to other, more pressing matters. But in the times that a fresh selection wasn't available, Squalo found he was often chosen as the next best thing. Not that he usually had a choice in the matter (had he been given one, the answer would have invariably been "no"), and often found XAXNUS also in likeness to a cat in this; you simply could not say no to one, and if you happened to, it not only would not listen, it would steadfastly pretend you didn't even exist. Like any big cat, he had a tendency to objectify you; you were, really, just something to satisfy his needs.
So, Squalo found that, after resounding refusals, and even violent physical rejection, no often meant yes, except more exciting, and that beating Squalo within an inch of his life before fucking him usually only meant more pain for Squalo in the end. It didn't happen often, because they weren't often in a situation where they couldn't access women for long amounts of time, and XANXUS could usually at least wait until the job was over. But it was still often enough that he found himself completely naked in a shower stall, one hand against the wall while the other pressed his face in an almost womanish gesture, XANXUS thrusting into him, blunt nails scoring Squalo's sides, growling like an animal into Squalo's ear. It didn't matter if Squalo came, though XANXUS never finished before Squalo, anyway, and so the younger man was left clenching his teeth with hot water rinsing away the mess, and XANXUS growling trash talk at him.
And, much like a cat, didn't care who saw him doing any of these things, even to Squalo, except, that, as he threw a bottle of soft soap with enough force and accuracy to kill at Belphegor (who had woken in the middle of the night in dire need of a toilet), another person in the room was distracting. Squalo, who had cared, had quickly lost any desire of the situation whatsoever, but couldn't leave, and was forced to endure for the length of XANXUS's resistance. It wasn't fair that XANXUS could last so long, anyway. (Squalo had come by the end of it, anyway; what could he do, XANXUS balls-deep inside him).
As they got older, and thus supposedly more dignified, XANXUS did not treat him as poorly as he did when he was younger; perhaps the thrill of fucking Squalo in a public urinal (this one had been rather a point to be proven to Squalo than anything else; he could still do whatever he liked wherever he liked to Squalo, and if Squalo thought differently, to stop him. Squalo hadn't been able to stop him, and was bent over a sink with his face smashed into a mirror, face scorched and blinded by the Flame of Wrath recently applied to his optical nerves) having lost its charm when the brat 10th had come in with a solemn face. He hadn't actually said anything, but, for whatever reason, having a twenty-two year old (Squalo had been at least that old when he started doing shit like this) stare at them with such agonized eyes was like suddenly seeing all the people they had ever killed in the bathroom with them at once.
Needless to say, things quickly got very awkward, not the least of the reason why being that XANXUS had shortly attempted to kill the brat. Upon failing to do that, he had beaten the kid (who, strangely, had seemed to allow this to happen) nearly senseless before leaving. The night, XANXUS would later say, had been quite enjoyable.
And, like a cat, was often spoiling for a fight and to prove his birth-given right to dominance. Even as he got older, had Sawada been in the room, his continued existence only seemed to serve as a permanent reminder and reprimand for XANXUS (who could never quite work past the fact that he was never good enough, never pure enough), and the only way to solve this existential problem was to try to kill him. So, in all honesty, it only got worse when he got older.
Squalo and the half-wild delinquent storm guardian would always be forced to pry XANXUS off the smaller, younger youth; sometimes it would be as simple as two fingers to the kid's chin, gripping too hard (Tsuna invariably never moved away from these touches; he didn't desire them, like Squalo did, but he didn't fear them, something Squalo always found stupid and incomprehensible), murmuring past remembrances like a revenant. Sometimes, however, he could be found straddling the boy's body on the ground, with both hands around the kid's throat, squeezing, Flame of Wrath glowing between his fingers, Sawada choking in increasingly pitiful and dying gasps. His hands would struggle birdlike, with the unconsciousness of choking victims often did, against XANXUS's arms until he blacked out. Whatever XANXUS gained out of these types of encounters, Squalo did not exactly want to know, but knew anyway, uncomfortable, now, with that sixth sense of his, that by looking at XANXUS's body posture, he was enjoying himself, and enjoyment was never purely distinguishable from one another. At least, for XANXUS, who always couple violence and sex (those would also be the nights Squalo invariably always found himself on his back, choking gasps forced from him as XANXUS thrust into him).
One of these days, Squalo told himself, he'd have to take the fucking katana-brat aside and tell him to teach their Boss some fucking self-defense, because no amount of Vongola Intuition was going to save him if he didn't fight back.
But, in the end, as XANXUS cradled the brat 10th's face in large, scarred hands, and murmured what sounded like regret rather than invectives, with his eyes over-bright (perhaps from fever, perhaps from moisture that had collected there) Squalo supposed he'd never really know everything about his Boss. Not really.