
MAJOR SPOILERS:
It’s not a yaoi. Having characters that happen to be male and have sex doesn’t make them necessarily gay. Sangwoo was never gay and is using yoonbum as a replacement for the lack of love his mother gave him because they look similar. It’s not love at all nor does he care for bum. And instead of asking us to find it for you, search it up yourself. You’re the one who doesn’t believe the information. It’s youre issue so you should be the one to disprove us instead of making us prove ourselves. She’s said it on multiple occasions and I’ve even heard that apparently bum might actually be sangwoos step brother which explains why bum looks like sangwoos mum. There are so many scenes when you can tell that sangwoo just doesn’t care and that bum is just a hole to him. He’s straight and he always has been. Bum may be gay or bicurious cause he did do a B&E out of his obsessive “love” for sangwoo but one sided love doesn’t make a BL either.

But since you wanted some proof, here’s what I found cause I cba to find each and every source so find it yourself from this.
https://www.reddit.com/r/KillingStalking/comments/k3omra/killing_stalking_is_not_a_bl/gexsv0i/?utm_source=share&utm_medium=ios_app&utm_name=iossmf&context=3

There are q&as in between the seasons of the manghwa. You look through them yourself. Being in denial about this just shows that you either haven’t read the story at all or your too immature to even read the story at the moment. They only fuck twice and the second time you can definitely configure to why this is indeed not a yaoi. gooday

The q&a's? That's your 'end all'? Bitch, who cares what the author said when what we see is just obviously gay. It's not like there's nothing there and the author is saying no, they literally have sex and Sangwoo lusts after him. There's a whole scene where he goes to a gay bar because he questions his sexuality thanks to Bum! "Denial" indeed... if the author didn't want it gay then they should've written it that way. They wrote it gay and looking at all the gay sex and saying "that's not gay" isn't an argument.

yaoi doesn't mean the character are necessarily gays, only that there are sex scenes between men. I don't search it by myself because i wouldn't find anything. I follow the author since January 2017, I met her in person twice and I read all the interiews and she NEVER said KS is not a BL (actually the opposite). I can link you the official q&A where she said why she chose BL as a genre for her first work. I can link an interiew where she said the story is not just violence but also love, and the q&a where she implies Sangwoo loved Bum.
Bum is not Sangwoo's stepbrother, it's another fake rumor!

Bro I’m done arguing about this. I was reading this since 2017 as well, not that the amount of time reading it even fucking matters. In the q&a the author explains why she was forced to put it into the Yaoi category. It was supposed to purely be a psychological horror story, but since she made but have a crush on Sangwoo, making it a yaoi was better for sales and marketing. I enjoyed the story throughly, but just because Sangwoo was calling bums name at the end doesn’t steer from the fact that the story was about a serial killer and a stalker that were too mentally unstable for love at all. How did you even meet the author anyway, she hasn’t even revealed her face or real name? Whatever believe whatever you want, I can’t say I wasn’t in denial when reading it while it was still updating either.

"It was supposed to purely be a psychological horror story, but since she made Bum have a crush on Sangwoo, making it a yaoi was better for sales and marketing."
So it IS gay and she made it gay. There, done. Her original intentions are irrelevant to the topic of contention here. Let me give an example to highlight the lack of logic in saying Sangwoo wasn't gay:
Your argument is the same as citing cut content in a game within a talk of in-game lore.

The story has always been in the BL category on the official site since the first day it came out. They kiss and have sexual intercourse since the first chapters! In the Q&A she actually explained she chose this genre since she was exposed to it since she was young!
I met her at comic conventions when she came to my country, google Koogi at Luccacomics 2017 and Koogi at Etnacomics 2019 if you don't believe me. I saw her in person, I asked her questions, I have her autographs :D
Guys the author said themselves it’s not a yaoi and shouldn’t ever be treated as one.