Yes, It's Me. The Obsessive Side Top summary:

One day, he suddenly became 'Ha Jin' a love-blind sub-protagonist in a webtoon. As he inevitably becomes involved with the main protagonist, Sun Woo, he becomes more and more immersed in the atmosphere and starts talking nonsense... “Sun Woo, are you a good kisser?”"Why do you want to know?" "Sun Woo, why are you so seductive?! If you continue like this, oh, I'll end up liking you!"The revolving love story of Sun Woo, who slowly falls in love with Ha Jin, and Ha Jin, who is a master of clueless flirting.