My childhood friend suddenly became transgender/changed genders. What do you think I should do?

That's right, yesterday should have been normal. I was supposed to have a light phone call with that guy, talking about novels until his parents took away his cell phone. So why on earth is he—my childhood friend—calling me up saying "This is terrible! Kazuto! I've turned into a woman!" *This story was written because the author thought "Wouldn't it be interesting if someone close to me experienced gender transformation instead of me?" Please don't expect too much, as this is poorly written.