[Micchi tries not to slap his palm into his face. It's not a dumb question - not at all! Some people are confused for a long time about who they like, or even if they like people that way at all! It's far more complex than Philip is going to get from books. And this is all stuff Micchi needs to get across to him.]

Well, boys and girls liking one another is the common thing, so it's assumed to be the default - practically the only thing, as you're already aware. [Micchi looks pointedly at all the other books Philip had been referencing that clearly hadn't talked about alternate sexualities at all.] Most people just accept that they're going to like the opposite gender and that's it. Mmmm... [Philip is going to want specifics.] I guess it's things like your heart racing when you see someone, or getting nervous butterflies in your stomach. Or if it's a much more physical attraction than anything else then your dick will respond.

[Dear god, don't say Micchi is going to have to explain masturbation to Philip too. Not that he'd entirely mind...]