Responses
I think K gave him a laced cigarette so thats why Gusam doesn't remember anything.
But that's only a hint. This webtoon didn't elaborate who's the killer and the back story why Gusam is in the murder place （￣へ￣）
But who's the killer? Why is Gusam found himself there in the murder place? What's up with K? Here I thought that Gusam will be found not guilty. But noooooo （/TДT)/