They will seem enigmatic. It will feel as though you are being swept off your feet. You will experience a feeling like you are in a romantic movie, yet you will feel at the same time that you don't really know them, they seem to keep you at arm's length, their facial expressions don't seem to match their words... but no matter, you're having the time of your life, and every minute with them (at first) feels like a huge dopamine hit. It's a guilty pleasure that you can't stop coming back to. They know exactly who you are and what you want, they've figured you out. You're so giddy, you are divulging every dirty secret and embarrassing anecdote you can think of. Meanwhile they're storing all of it to use against you later.

Tldr: they make you addicted to them with love bombing and intense attention showered on you. You know it's happening too fast, but you don't care, because it feels great.