Twinkle Stars, one of her later manga from after the original Furuba. I liked it at first, but the characters I liked early on wound up being disappointing to me, and towards the end I got revolted by the way the narrative treated a specific character. The lack of basic empathy for the character in question made me so angry I actually threw the book at a wall! (Sorry if I'm being vague about it here for now; there's only so much mental energy I want to spend thinking about a series I hated).

That's not to say all of Takaya's non-Furuba series suck -- I liked what I read of Liselotte and Witch's Forest fine -- but Twinkle Stars soured me so much that it makes me worried that, if I ever rewatched or reread Furuba, I'm going to notice things that either haven't aged well or just don't sit well with me anymore. =/