If they did a sex ed day at Yasogami High chances are Kanji skipped it the way he skips al his classes. Add in his dad dying when he was eight and it's a pretty safe assumption that he's never had any sort of talk about these things with anyone. He almost does his usual frantic blushing and retreating thing but you know what? Jack has been really freakin' cool about all this stuff so far and he's never made fun of him of made him feel bad about himself and this is probably the only chance he's gonna get so screw it. Time to be a man and ask the hard questions!
"I, uh, don't know anythin' about that kinda stuff. Like any of it. At all. Nobody ever told me. I kinda, uh, looked around the other day when they made me a girl but that's basically it." He's blushing alright but at least he's meeting Jack's eyes which is a good sign he's taking this seriously.