sunny boy books

My name is Azami Yuki, I am a 4th semester student and a boring, ordinary guy, but somehow without realizing it I have moved into an upside down world where the ratio of men to women is 1:5, not only that, as soon as I opened the door to my apartment. I saw the sight of a woman who had almost the same hair color and facial features as me changing clothes?! what is really going on, someone please explain to me?!