Hm, as far as I know, it depends on the country.
Like, Rinko is right. She's technically the adult in this having a relationship with a student.
Now disbarring whatever is the legal age for whatever country, because that is such a reductive argument,
Rinko is the adult in the relationship, it looks wholesome, whatever, but end of the day, she's the adult that should know better than to get involved with kids still developing their own world views and opinions. It's a matter of having someone taking advantage of a minor, no matter how you slice it, male or female, :/ like personally having known teachers who came out to have had relations with students, both men and women.
Even if the woman had some stuff she was dealing with, having relations with a student, she's still the adult to know that that sort of relationship isn't tolerated
I still appreciate the series, btw, lol, still, don't defend teachers who have those relationships with students. Yeah, in some cultures, the student (like if it was a guy who got it in with the hot spanish/English teacher), that sorta thing does affect the guy to end up a total dick bag. It falls on the educators causing this to happen and, pinning it on students makes it much worse in terms of what it does to them as people, especially since they're so young.