Somewhere in the middle of the episode, right around when Kyousuke entered the party I was wondering if the director kicked the writer in the ballsack and ordered him to redo the final half of the episode altogether.
Personally I think that somewhere along the line after treating Manami like crap in their house, Kirino realized how much of a jealous bitch she was, and after that also began to realize that all along the while Kyousuke's been taking bullets for her and tempting karma along the way yet she was mostly ungrateful. As I said before, she may be emotionally blunted, by she still possesses some degrees of human contrition, thankfulness and empathy. The fact that she managed to remember how good Saori and Kuroneko were to here at least shows she is able to think of others besides herself.
I actually think that the eroge as a gift for him fits perfectly with her character and her approach towards her brother. In the end she's still the anime/eroge fangasmic fangirl she has always been and Kyousuke has grown to accept and love (as a sister, get your mind out of the gutter
), and this is still one of the things that connects them. Heck if Kyousuke's been playing eroge now and not simply because she told him too, it would be sort of a perfect gift in that regard. Of course she did say to him that
"take care of them as you would me" so... uh... yeah interpret that as you will.
The episode managed to give us the Dere that has been lacking (for the most part) in her Tsun, so as Triple R said her character has rounded out towards forming the full circle that would make her worthy of the Tsundere label. Manami really is a bro, and she reminds me of an old friend of mine, minus onii-chan anyway. We never really got together but we stayed very close friends. Manami would make a fine wife for Kyousuke IMHO.
And like Klash my only real complaint is the lack of a connection between Kirino in the first half and Kirino in the second, which makes it feel a bit like a 180 if she wasn't still being true to her usual self. On the other hand it manages to show that Kirino HAS changed a lot over the weeks he's been helping him and has fully acknowledged it, so while I think this may have been good as the series finale, it still sets up for a very good finish even if the middle of the series was so-so.