Twenty-nine year old female tutor, taking a break from studies, looks at young male protag-kun with a crazy spin in her eyes and asks to see his penis, which later escalates to "sexy happy fun time".
IRL: 911 Red Alert / Child Protective Services Open Up / Deviant Sighted, etc.
IHU (In the H-Universe): Protag-kun graduates to being a Man Of Culture and/or Lucky Bastard.
"She's not watching me study, she's looking at my penis"? So basically a normal day in the Hentai world, got it.
Still, what a nice guy, showing her his dick after she kind of...actually begged him to do so. And, well, from there Hentai just takes its natural course.