Man, trying to remember all the key characters from 'Love Me Later' is actually harder than I thought because the cast gets pretty big, but the core ones are definitely Leo and Clara. Leo's this incredibly guarded guy, a real estate developer or something, who's built literal walls around himself after past trauma. Clara's the interior designer brought in to work on his cold, empty mansion, and she's all about warmth and light, which sets up the perfect enemies-to-lovers dynamic.
Beyond them, there's Leo's business partner, Ethan, who often plays the comic relief but also acts as the voice of reason, pushing Leo to open up. Clara's best friend, Sophie, is her sounding board, the one who encourages her to take a chance on the emotionally unavailable guy. A character named William, who I think is Clara's ex or a rival designer, shows up to create some tension and make Leo jealous. The late-game addition is probably Leo's estranged father, whose reappearance forces Leo to confront the root of all his issues.
Honestly, while the side characters serve their purpose, the story lives and dies on the chemistry between the two leads. Their push-and-pull, with Clara slowly chipping away at Leo's armor, is the whole point. I sometimes wish Sophie had more to do beyond just giving advice.