This garment is technically not underwear despite the tag, since the modern take on bloomers usually has them in addition to a pair of knickers of some sorts, not alone. Still, I couldn't bring myself to tag them, albeit very open for interpretation, under 'trousers'. And I realized I have seen very few pieces of underwear which would clearly speak to me as being alternative in any way.
This pair of bloomers is elementary Lolita stuff, both Sweet and Gothic. (Mostly Sweet, yes, agreed, but these come in black, too.) A must-have, if you will. I hear bloomers such as these are fairly easy to sew yourself, if you are so inclined and, incidentally, every single person I know to incorporate Lolita-ish elements in their style happen to know how to sew clothes. It must be due to how unbelievably pricey these things can get, the bloomers you see above being no exception.
Available here (under the 'Skirt, Drawers' section).