Hell, there's places where the age for marriage is disgustingly low here in America.
The fact people are fighting so hard for this honestly tells me a lot about them.
It says nothing about them, but trying to use veiled ad hominem attacks says a lot about your argument.
The way I see it, there's no question that what the teacher did was wrong morally. She seduced her student, and I think she got him intoxicated with that intention and took advantage of him. There's no issue if people dislike the character for that. BUT I also don't think there's an issue if people still like the character. As the translator pointed out, this is considered erotica. No shit people are horny for the characters, that is the purpose of erotica.
But there's something I really hate when it comes to this "rape" discussion. Even if this is erotica I don't think theres anything wrong with discussing whether she's technically a rapist or not but at least do it properly. If you don't care about age of consent laws then you don't have a fucking argument. Don't bring up the MC being a minor and then proceed say you don't care whether he had the ability to legally give consent in the country he lives in. You're just yapping out of your ass.
I shouldn't have to explain this but rape is by definition unlawful. You're not more moral by throwing that word around willy nilly and then declaring yourself to be above anyone who would dare question it. I'm not even saying that whether what she did was wrong or not rests on whether it's illegal or not. And it may still be some form of rape other than statutory, but make those arguments if it is.