In Episode 6, titled the line between Hong-jo’s feline instincts and human emotions begins to blur as he realizes that his existence depends entirely on Sol-ah’s proximity. The Midnight Realization

To help you continue this story or build on the characters, tell me: (immediate realization or denial) Jae-seon's role (jealous rival or suspicious investigator)

The episode opens with Hong-jo waking up in the middle of the night. For the first time, he feels a literal weight in his chest—a human ache. He watches Sol-ah sleep, realizing that when he is a cat, he sees the world in shades of instinct, but as a man, he sees her in shades of longing. He starts leaving small "gifts" for her around the house—not dead mice, but things he thinks a human woman needs: a lost earring he found under the sofa, a warm tea bag, and a neatly folded scarf. The Conflict of the Collar

Sol-ah is still reeling from her complex feelings for Jae-seon. When Jae-seon visits the house to check on the cat (Hong-jo), the tension is thick. Hong-jo, in human form, hides in the closet, listening to them talk. He hears Jae-seon warn Sol-ah not to get too attached to "things that eventually leave."