Why does Kagami feel necessary to emphasize that she is a simple-minded person?

Question

This has been on my mind for a while. In Lucky Star Episode 18, Tsukasa Hiiragi lightly expressed her desire for having a pet dog. But she quickly got her dream crushed by her sister Kagami, who warned her about all kinds of problems that would be faced by a dog owner. At that point, Tsukasa had to agree with Kagami, and said something along the lines of "you really know much about this, sister." On hearing that, Kagami suddenly became bashful, turned her head away and said: "In the end I am also a simple-minded person, that's why I looked those things up".

It is this reaction of Kagami that does not make sense to me. Of course, I know that Kagami is a Tsundere kind of person, but I still see no reason to feel ashamed, or to emphasize your simple-mindedness here. After all, the difficulties of dog-raising that Kagami mentioned (walking, feeding, difference between a puppy and a grown-up dog etc.) do not seem like something that a high school student should look up to know, and no one would say that knowing these things stop you from being simple-minded.

Am I missing something deep here, or is it just Kagami designed to be over-reacting?

Answer 1

Kagami sees her simple-mindedness as something desirable

To explain a bit more, in that scene Tsukasa very innocently expressed her desire for a pet dog and didn't even consider the possible down-sides because of her air-headed character and the fact she was excited about owning a dog and single-mindedly chased after what she wanted.

Now, Kagami's character throughout the series has been established as the more forward thinking of the two sisters, but she doesn't want to be! When she reacts this way it is expressing how she wants to be like her sister, she tries to stave off the comments about how responsible she is by saying that she was just the same as her sister and innocently wanted a puppy too! And she was only the voice of reason here because she had been enthusiastically and innocently thinking about it for a while.

Throughout Lucky Star, it is a running gag that the sisters both envy the others personality traits, and this scenario seems to be an example of that. (you can also see here how Tsukasa also wishes she was more responsible like Kagami)