As much as I don't like Tessa, she is actually perfect for the role in the Sousuke, Chidori, Tessa love triangle since she is the complete opposite of Chidori. Tessa is quiet, shy and usually keeps to her self but Chidori is loud and obnoxious. As TwisT already said, Tessa is too timid and shy for my taste.

Even though Sousuke has feelings for both of them, he can never make a move with Tessa because he has too much of a respect for her because she is his captain. However, since Chidori is not only his mission, but a very good friend, he feels more easy with being around her. But even with Chidori being his good friend (probably his best school friend), he still can't make the right move with her since she is a mission first, then a friend. So pretty much his duty gets in the way of him expressing his feelings and the love life he has, which will probably be shown in TSR seeing as how the trailer and previews show lots of what's in the novel.

Oh also...

Twirly twirly...