After School Nightmare Volume 1 - Setona Mizushiro

You have just awakened to find your darkest, ugliest secret revealed to classmates who would do anything to destroy you. This is what's happened to Ichijou Mashiro, whose elite school education turns into the most horrifying experience of his life when he's enlisted by a mysterious school nurse to take an after-hours class. Only those who pass the class will graduate, and the only way for Mashiro to pass is to enter into a nightmare world... where his body and soul will be at the mercy of his worst enemies. Can Mashiro keep his life-long secret - that he is not truly a "he" nor entirely a "she" - or will he finally be "outted" in the most humiliating way possible?