Nah, I'm not offended. This is a sensitive subject. Frankly, I'm not sure how laws vary from country to country, so I don't know where exactly the bar should be set. There are a lot of anime girls who look similar to the pic you describe that would normally be as acceptable as hentai gets, like Miku from Vocaloid. She has roughly those same proportions. The difference with Mitsuru is that we know she has a developed body at the age of 18 so it makes that pic highly questionable.
So, I'm really on the fence with quite a lot of those types of pics.