Well, I root for Itsuwa and Kanzaki (I can't take her out the list since the plot indicates future character development), even less Index because of Vol.1 epilogue and due her being Touma's emotional support and motivation por most of the events that linked him with magic. Just mind tsunderes fandom raging if Index or other girl ends up with Touma, something wouldn't be suprising.
Poor Himegami
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I wonder what kind of relationship had Seria Kumogawa with the old Touma? Some lines seems to indicate she views him more than as a friend and knows about his memory loss to some degree.