I asked someone at the Baby store about the specifics: Basically if you spend at least 15000 yen, you can receive a pair of these slippers! And yes, they are ADORABLE in person.
If you order from tomorrow (japan time) you should get a pair! but you know, with the addendum that, "as long as supplies last!" =D Both online orders and in-person purchases are eligible for the giveaway!
Happy shopping =D