Weapon Master and Beautiful Elementalists

Chen Yu'an was an ordinary high school student. Then one day, his classmates, teachers, and everyone in the city... all became beings like the shambling undead in zombie movies. (Note: In this book, the walking dead are called Corrupted Creatures.)

At the same time, among the human survivors, some awakened as Elementalists, able to use elemental magic. (Note: Corrupted Creatures can also use human weapons, and some are Elementalists too.)

But why did Chen Yu'an become a woman when he awakened as an Elementalist?!