Is it unique story? Nah, it was so-so, but the art is superb and magnificent. Overal were good, the way the story being executed were better than awewere story of body swap.
Now, at chapter 3 my guess the reason she (the one who dwell on male body) was hate her life or at very least dissatisfied by it, so, when she got "new life" she's choose to ran away from her previous self life. That's why she's so acceptable with her current life.
And about the female body classmate was the most obvious thing, he love her either he's her girlfriend or simply best friend who had feeling towards her before the body swap.