She was briefly in the first season and yes there is a second season called 'Nisemonogatari'. This season has more of Karen and her sister Tsukihi Araragi and they were called the 'Fire Sisters'.
If your off to the torrents, grab the 'Commie' sub releases as they were better than most.
Also Tsukihi should be out soon for pre-order as well sometime soon.
And YES!!!!! WHERE IS BLACK HANAKAWA