Is this really official art? Definitely seems fan-made with the over sized knockers (even for the character.) Doesn't seem like something the original artist would do. Also pretty risque for a shonen series.
Well, I added the "official art" tag. Someone can remove it if it turns out that it's not.
Fan artists put their own spin on a character's design to (somewhat) call it their own work. This is unmistakably Kubo's - the face alone is a dead giveaway.
Yeah, this is Kubo's drawing. This slip was included in the latest Japanese DVD release of the anime. That, and nobody draws these eyelids, lips, and breasts the way Kubo does.
Someone should upload the complementary pic of little Nel that goes with this. XD It's pretty cute.