Need help finding a Manhwa. (18+ One)

The basis of the comic is a guy who is a bit shabby looking but his dream job is working at a well known modeling agency. He actually gets the job and is an assistant. He goes to a bar with his friend and a random attractive woman takes him to her room, but she drugs him with a drug that seems to give him increased performance during intimate moments. He ends up changing his look and becoming more confident. (The drug hurts him the more he engages in sex but doesn’t show signs till the end) The model he works with all play small jokes on him but throughout the story he ends up in a sexual encounters with all of them. Except the woman he actually likes. He eventually gets healed by the doctor he visits who track down the maker of the drug he was given. He also ends up marrying the woman he originally liked and gets a happy ending. All the models attend and it’s just one of the classic harem endings.