I absolutely love the relationship between Kippei and Yuzu. It's unique and heartwarming. However, I can tell the author didn't think the story through. The mangas that I love have characters who are naturally complicated. Their past experiences define the way they respond to the world around them. In this story, the author had stereotypical characters that had complications added to them as the story went along; complications that didn't match the way they had been behaving at the beginning. It wasn't convincing, and I didn't feel a connection to any of them, except for Yuzu.
That bothered me a lot, because I really liked the story. The elder sister confused me the most, because the author reveals something very serious about her halfway through the story that doesn't make sense. If she really were a person with that issue, why would she make her younger brother the guardian of Yuzu and not herself? Wouldn't she feel an intense longing to take care of Yuzu?
I think that was the moment where I stopped being interested -- because I realized that the characters were lacking substance. Their emotions and behavior had no reasoning -- and if there was a past experience to fall back on, it didn't make sense, or was too weak to be believable.
I think the author should revisit this manga -- if not for the characters, at least to add a satisfying ending.
I admire the drawing style, the touching moments (that were the most realistic parts of the story), and the story itself. I think the author did a good job and has ample talent, but needs to try a little harder. If she does, I imagine she will have no problem putting me through a roller coaster of emotions.