1. Reimu is saying, "It feels like I'm flying!" This is something that girls commonly say during sex in hentai anime. So when a yukkuri is saying this while rubbing cheeks with her mom, it's supposed to be good and H. : )
2. About the u-packs: Yuubin is Japanese for mail. "What is Yu-Pack?? Yu-Pack is a domestic mail service, sending different types of parcels all over Japan. There are many discounts provided. Please check at our offices."
That's right, but when you put them all together it just says "it feels like I'm flying in the sky!" Maybe I haven't watched enough h-anime but I never heard that expression before. :p