You’re the best person to know what’s going to aid your story as we only get snippets. The only reason I suggest it not being the date is if she is the ultimate love interest, it seems controlling to change him and in some way less heart warming.

If alternatively he was a lonely man pining after someone he couldn’t express feelings for, the new world might help him achieve that. Maybe he gets set up on a disaster date by his friends because he can’t interact with women very well.

If his date at the theatre was a painful blind date – I could see her causing the supernatural change that leads him on his quest – ultimately leading him to true love with someone else.

Like I said though – you’ve got the bigger picture in your head.