For me, it's Towa.
It's a difficult question to answer because she frequently gets new designs with each story arc (or game) she appears in. However, until her latest appearance her trademark accessory was the huge blue ribbon that she wore in her hair. It was present in the five Cold Steel games and Tokyo Xanadu.

For me, it's Towa.
And she is! Trails beyond the Horizon is releasing early next year, January I think.

For me, it's Towa.