Lesson is this, Kakashi read dirty books. Porn/erotic material lessens your ability to have meaningful relationships.I mean it would of been cool Kakashi ending up with someone and having kids, Kakashi had many choice to choose yet chose no one. Kakashi had these to select
Tsunade
Sakura (although too obsessed with Sasuke)
The girl that spoke to Kakashi at obito grave, can't remember name
There maybe more, I just can't remember
He was probably traumatized by the whole Rin situation and just gave up on love.Lesson is this, Kakashi read dirty books. Porn/erotic material lessens your ability to have meaningful relationships.