
Honestly I don’t like the Sunbae (due to him never making MC feel good and caring about his own pleasure, confirmed by MC wondering how sex felt this good when he was with the creepy dude) but I’m not a fan of the creep guy either.
Let’s see how this will end. I have a feeling the creep is the endgame though. It’s 95% the super toxic/inhumane (literally inhumane here/non human) guys that are endgame.

That's right they're both toxic aren't they? The difference being, the sunbae is an asshole but the black hair is sinister. And they both SELFISHLY want the uke to themselves. They are just going about it in different ways.
Part of what will be the sunbae's growth in the story is his admittance of his feelings for the uke and gradually treating him better. Remember they started out as FWB. He will definitely try to protect the uke from the black hair lead.
It's the opposite with the black hair lead. He already treats the uke well, but when he finds out the uke is still seeing the sunbae, he's going to be really scary. He's going to try to make the sunbae dissappear and the uke will not like that. I think part of his story as said, at his core once he realizes the uke isn't lonely anymore, he'll let him go.
but we'll see. I'll remember this conversation.

Hold on, what do you mean you’ll remember this conversation? That sounds so menacing.
And yes both are toxic. However, I do kinda like the dynamic more with the Sunbae. I just don’t know if colored hair guys are going to be endgame, it’s rare compared to the black haired MLs.
Both are going to be scary when they know about the MC having each other, but since the Hyung isn’t human, he’s obviously going to be scari-er.
I honestly also forgot how the hyung came to their family, or he’s always been there but got possessed. I’m not feeling like rereading to see, I got a bunch of other to catch up now.

Also is there more scenes with the Sunbae? I feel like there is, so you may be right that he’s the endgame bur let’s see. Istg there’s always a twist…and the black haired dude has some face the author worked hard on, I doubt he’d be wasted.
And authors usually try to make the ML more powerful, so the hyung being a monster is already another level to a human capabilities probably.
I agree. 50/50, it’s kinda hard for me to predict who’s endgame due to the amount of stories I’ve seen have twists. There are stories where the author makes us think we know who the endgame is, then Bam.

I feel like initially there were more panels with the sunbae, but we'll probably get more of the hyung too as the love triangle deepens and the author delves more into his background.
I know the cliché characterization of the main uke and seme in bl stories you're describing. However, I just realized who this author is, and she's not so black and white. There's actually substance to her bl stories. This story can really go either way.
I'm team sunbae. My take on this story -
I think the other guy will serve as a catalyst for the relationship between the uke and sunbae. I think it's their love story. The author is purposeful in making the black hair lead seem like a villain because he is the final* antagonist. I think the uke will choose the black hair lead for a while, even when he finds out he is not human. He'll try to give him the benefit of the doubt and keep his promise with him.
Meanwhile the sunbae will slowly come to terms with his feelings for the uke and try to protect him throughout the story. The uke will go back and forth, and I believe the black hair lead will eventually try to harm the sunbae and the uke will intervene somehow. Things blow up further and the black hair lead will come to some self-actualization and realization that the uke isn't lonely anymore and has had someone, then he'll go back to where he came from.