Annyeong, I'm a fan of this drama and like all, I'm dying of the suspense as to who the killer is. Thus, I decided to check out this site for updates. After last night episode, pls allow me to share my guess. I'm pretty sure the killer isn't HS (Heung-Sik aka the CCTV installation guy). This is because Hyang Mi called the guy in the dark alley "Ahjussi". As we all know, this is term used to address someone who is an elderly and HS seems younger than Hyang Mi. My guess is this elderly guy named "Han Tae Hee". Reasons being:
1) The dry chillies was next to Hyang Mi when she was led to the room by the "Joker". And we know the guy that offers her the accommodation is Joker because of the burnt mark under the table. In ep 1, we saw him sunning the same dry chillies in the alley and it was run over by a bicycle when Dong Baek first moved in.
2) In ep 8, Dongbaek refused to close her shop after the wall scrawling as an act of defiance as she believed that "Joker" will be checking her out soon to see her reaction to it. And later, we were brought to the scene where a group of patrons were gathering around the newly installed CCTV, one of them was Han Tae Hee.
3) In ep 8, he was one of the guys in captured in the CCTV video footage which Yong-sik was studying. According to Captain Byun, the Joker must have saw the CCTV being installed and he would have been one of those in the video.
4) In ep 9, Dongbaek flashed back to the time where she first started and the first two customers that came in are Han Tae Hee and Song Jin Bae. That scene somewhat felt that there were more to it than just two ordinary patrons. I believe the "Joker" wanted to check out Dongbaek after learning of her identity from the press (after his last killing) just like he came to check out Dongbaek's reaction after scrawling on her wall.
5) Lastly, Han Tae Hee fits the term "Ahjussi".