The shape looks like "XX XX XX XXXX XXX" but I couldn't really find anything that matches, so I'll go with
1. "Please stay with me" or
2. "You are so beautiful" or something similar for now.
I don't think he confessed already because he should know he would get flat out rejected, probably making Kim Dan distance himself and quit on the spot when the contract is over (I don't think Dan would do that but Jk might expect that).
Since it's the first time he's showing anyone even a little appreciation, he's most likely blushing this hard just from the tiniest revelation of his feelings, which I expect to either be an appreciation of Dan or (regarding their conversation) his wish for Dan to keep working for him - but a bit more heartfelt.

Today we're guessing what's in the blurry bubble. The winner will receive the prize: the name "fortune teller witch" of 2025. Get ready, set, and go!
(¬‿¬)