What Do These Three Have In Common?
It's pretty obvious. Sanemi Shinazugawa hates each of them terribly.
Now, I can already hear your protests, because...
Obviously, Sanemi doesn't hate Genya. That's his beloved baby brother! The only reason he does anything, the thing that gets him up each day, the last face he sees before he goes to sleep, his precious!
And Obviously, Sanemi doesn't hate Masachika. That's his (dead) best friend! The one who saved him from living the life of a feral vagabond, catching demons and stringing them up by their toes to burn in the sun. The one who introduced him to a trainer, brought him into the Demon Slayer Corps, and eventually died to save his life!
But Giyuu, yeah, he most definitely hates that guy.
I know many people like to pretend that it is that straightforward, but to do so requires ignoring the complexity of Sanemi's character, because here's the thing: Sanemi has got his wires all kinds of crossed when it comes to love, platonic or otherwise.
All you have to do is look at his canon interactions with Genya (right up until his imminent departure from this mortal coil) to see that Love is not straightforward for Sanemi. It goes without question that Sanemi loves Genya (do you see the love in his eyes in this picture?)
And yet he abandoned him for appr. eight years, rejected him when he eventually came looking and found him, disavowed their relationship entirely, told him he would break him beyond recovery if he didn't back off, and tried to literally blind him. He flat out says he would do anything short of MURDER to stop him. (Don't worry, guys. He did it all out of love.)
Now if you're thinking, Aves, that's a special case. He had his reasons. Genya was an exception. He was treating him with so much apparent hatred because he was trying to protect him! Okay...?
Well, fine. So let's look at Masachika then. We all know that Sanemi cares about Masachika, and loves him like a brother. Yet in the Light Novel story, Signs from the Wind, we see a lot of Sanemi's introspection and interactions with Masachika - his best friend. And it doesn't look like love at a glance.
In just a couple of pages, we see ALL this: He tells him to "Shut up"; says: "Seriously, what is with you? You keep babbling on and on."; He feels 'ready to explode' because Masachika is annoying him; he's visibly irritated; he calls him a "Piece of Garbage" and a "Brainless dolt"; asks "What's his problem?"; he's Sick to death of him, and wonders "what, exactly, he had to do to get Masachika to understand precisely how unwelcome he was."
Can you feel the love, friends?
But we know it's there for Genya. We know it's there for Masachika. Sanemi is just absolute shit at showing the people he cares about that he actually cares about them. Why? Because, in Sanemi's own words: "He was determined to walk this bloody path alone."
It's because he cares that he pretends not to. Sanemi directs anger towards those he loves. He intentionally tries to push them away. The more he cares about them, the worse treatment they get. It's pretty clear why, I think. The first (but less important) reason is self-preservation, even subconsciously. He's lost people he loves before, and he knows how bad it hurts. If he "doesn't love them", then losing them won't hurt so much. The second (and far bigger) is to protect them from that same pain.
Sanemi knows that this life of Demon Slaying ends in an early grave. He can't stomach the guilt of hurting the people he cares about by subjecting them to his own death. He figures that if he treats them like shit, then they'll hate him as much as he pretends to hate them. He can go on fighting, protecting them from a distance. And then, when he inevitably dies, they won't have to mourn him the way they would if they had been friends, brothers, (or some secret third thing.)
Which brings us back to Giyuu Tomioka, Sanemi's beloathed.
Sanemi hates Giyuu. He says so himself in his own words. He only agrees to even try to spend time with Giyuu, begrudgingly, at the request of Master Ubuyashiki. He gets pissed about Giyuu's chilly attitude, and annoyed by his stand-off-ish-ness. When they spar, he suggests that they try to kill one another with their bare hands. It all sounds like hatred to me. Except, for Sanemi, when he hates someone, it often canonically means precisely the opposite is true.
Babes, I won't even try to convince you that Sanemi and Giyuu are actually head-over-heels-in-love with each other, okay? (I mean. They are. But I won't try to convince you) I'm just saying that Sanemi canonically treats the people he cares about most with the least amount of love and affection. So maybe, just maybe, the obvious hatred that he has for Giyuu isn't actually hatred at all.
