But, if what we're talking about here is "Awwww! Cute! Super-Cute!" moments (which is my interpretation of "fluffy") then I will have to go with another CLAMP title, one that (incidentally) overlaps with Legal Drug, Suki!
Suki: A Like Story is a three-volume series that centers on high-school girl Hinata "Hina" Asahi, an ultra-naive, bubble head, living on her own. This is one of the sweetest, most innocent, and clueless characters in the whole mangaverse. She could be sickeningly sweet, except she's also really, really funny in an ever-positive, always-sunny-all-the-time way. She "falls for" in her cluelessly innocent way, for her new teacher (a gruff and grumpy type, who sees her as a kid, thankfully) and hijinx ensue. We learn a little more about Hina's life and personality as the story progresses and she grows up just a bit.
And if that weren't cute enough there is a side-plot involving the author of a children's book, whose story about a grumpy bear and enthusiastic cub mirrors that of Hina and her teacher's relationship.
Suki is not the normal fare for me. It is really, really cute. But it is also very insightful and it always gives me a "fluffy" feeling...if there is such a thing. Fluff! Fluff! Fluff! (Bears are fluffy...)