What's this? No comments on this chapter? Huh.
By the way, this was made into the second half of episode 9 of season 2, so it ended up taking place before the arc about Shu's crush on Kyoko-sensei, which was episode 10. Slightly jumbled order of events, though there isn't much cross-over between the two events, so they really could happen in either sequence.
But, anyway, yeah, this is clearly a chapter about Haru getting to know the real Raku, instead of the bad image the rumors gave her. The fact is, she's spent all the years before this one that Raku and Kosaki knew each other in Middle and High School up until this year away at her own, separate school, living in its dorm (yeah, it's not really explained why she went to a different Middle School than her older sister, is it? feels a bit odd).
So all she has to go on are the bits and pieces Kosaki let slip about her 'crush' over the years over the phone and the nasty rumors she heard going into her first year of high school.
In any case, she's seeing just how earnest he is about taking care of people, and the fact he makes amazing food, even if she refuses to admit it tastes good but still scarfs it down eagerly. And how derpy and clumsy he can be, because he's nowhere near as well put-together to do the things she thinks he does.
And this new tsun starts to become a bit more dere.