Sokora Refugees manga volume 1

Kana thought her life couldn't get any worse - she was consistently behind on her schoolwork, she had no luck with the boys, and she was the only one of her friends who hadn't "blossomed" yet. When the new boy in class conjures up a portal in the girl's shower, she is transported to the magical world of Sokora - wearing nothing but a small cotton robe. Now, on top of landing at the center of a giant battle between good and evil, she finds that her body is beginning to go through some tremendous changes.