Slasherturtle

Hmm, it is just my opinion.....but I think he chose Senjougahara because the more he got to know her the more and more fragile he saw she was. She kept trying to hide things behind a strong facade and after knowing so much about her and helping her he decided he wanted to protect her. Though it may seem that Senjougahara can take care of herself, she really does rely on Araragi a lot and seeks comfort in him. At times Senjougahara may seem like she will kill Araragi without a moments hesitation like she often says, I think it would actually be very difficult for her if not impossible. Like they both say a lot in Nisemonogatari so far as I've seen they are both hopelessly in love with each other. Plus I think Araragi and Senjougahara understand each other and worry about each other the most.