how do i explain that my anime drawing friend needs to learn values?

you don't

>anime
Just give up.

>>2451130
show them good anime draws with good value statement that will inspire them.

>>2451130
anime is depraved, there are no values you can teach.

Buy them some good art books for their birthday or something and let them figure it out himself.
They simply won't understand it, you wouldn't have understood it when you were at that stage either.

generally not a good idea unless they ask, and if they ask you have to sugar coat everything. generally you can tell the people that actually want to get gud and you can give them the good shit, but in my experience most people want to live in their own little bubble. not saying you cant try of course, it's just that you might regret it when they get defensive