I like how you threw a very active and a very (supposedly) passive character together, and created some interesting dynamics between them. Plus, the cuteness. ;)
I especially enjoyed the "breaking out of her shell" ending, if you can call it that, although both endings are sweet, indeed.
A noteworthy thing: The opening screen (the main menu) really set up a nice mood. It was this screen with both its music and its simple, yet effective visuals that drew me in. Whoever designed that: Nice job, because first impressions count! :)
An unfulfilled wish #1: I would've loved to see a CG with both of them looking at those comets! I mean, it's even in the title! Like, it's in the title! But probably not in the budget? ;)
An unfulfilled wish #2: The art appears to focus on Julie, which is nice, given her looks and all, but I would've really liked to see more of Dina as well. She just seems more like "my kind of girl", I guess. ;)
Bottom line: Pretty decent job, I liked it. Will leave a few coins behind, because it's worth it.
Please keep creating!