While I'm a big fan of Kawai-sensei's work, I've never been one for teacher-student relationships - although I tend to make an exception for my favorite artists, this one I will have to pass on.
Don't get me wrong, it's a good story, and if you like that kind of relationship then its probably something you should really try reading - however, what got me was how the story changes almost drastically from the first chapter or two. It seems to start out as an older-younger guy relationship in a normal (non-school) setting. I liked that part, but it suddenly jumps almost too quickly into the student-teacher thing without warning.
Plus the relationship seemed to take a 180 overnight, from "I love you" to "they don't know each other". Add to the mix in that somewhere along the line they get caught in school grounds together, and that makes the last half more then slightly depressing. Since I'm not a fan of couple who spend most of the book forcefully separated (in some way), this hits a sour note with me.
In my opinion, the book seems to drag it out, although well written, I couldn't connect with the story. Plus, I still think the last half of the book was a bit too depressing for my tastes (and I'm not going into the legal technicalities that the teacher got himself into). That kind of thing gives me a headache, so I'm staying away from this one.
The book gets a 5, since I like Kawai-sensei's artwork, but I can't recommend this one out of all the others she's published. I'll say it again, if you like the teacher-student thing, then give it a go, otherwise keep looking elsewhere.