Well, i have not seen KnM, so maybe that is why i lack interest in their story
As Sorrow-kun said, they just didn't get enough attention to be interesting enough as a stand-alone story. It is a fairly weak side story, where the relationships between the characters is clear from the get-go, and they don't change practically at all.
Sure, Mika didn't turn out as flat of a villain as i thought she would be, but still ... it's hard to think of her as anything else when the only character development she had was revealed to us 2 minutes before her death. Doesn't help that 70% of Himiko's lines are "Kaon-chan...".
Perhaps i would be more interested in them if i would have seen KnM, but i have not
And judging by the majority of comments it was not that good anyway, so i doubt i will any time soon. Correct me if im wrong