Wow, I'm surprised no one has added a comment yet ! So, I first want to say that I really liked this story !
I don't think it's gonna be to everyone's tastes because of the specificity of the subject, by the way this is the first time I came across one like that (I think this is why it hasn't received so many good ratings). Well, I don't want to reveal the secret of Fuyuki, but what I can say is it's a deep and profound subject that is flirting with metaphysical issues. So if you don't like that kind of story, I don't recommend this to you.
But for my part, I really enjoy that sort of subject, but it has to be well treated, and that's the case here. The confrontation of Craig and Fuyuki's opinions is really interesting, I liked to see how Fuyuki changed slowly through contact with Craig. I also appreciated that through the story, sensei shows us how there's often personnal issues behind apparently objective thoughts and/or principles you can have about life in general.
Another good point of this story, for me, is to see Fuyuki overcome some of his strongest wounds. I always find it so deeply moving, it always make my heart melt.
The only bad thing is the end, and it really is very sad given the quality of the rest of the manga. The problem is that I found the end rushed. It's as if the author didn't found the point where Craig and Fuyuki's opinions would meet, and just ended putting away Craig's one, which is the most interesting I think. And so all the reflection there was before kind of falls flat. But I still rated it at 8 because even if the end spoils the atmosphere, the rest of the manga is so interesting that it's still worth reading. And I have to say that I don't usually rate a manga with a bad end this high, but this is an exception.
As for the art, I like the style even though I wouldn't say it's gorgeous, it is sweet enough to appreciate it. But even if the love scenes are well done, these are not the main topic, the story is really focused on the evolution of the characters.
So in the end, if you are open to mangas that are uncommon, and make your head think a bit, I really invite you to give this one a try.
PS: the description is talking about 4 chapters for the last version, but in fact there are 5 chapters plus a final one. So if you find it with only 4 ch. you'll know it doesn't end there. The final chapters are those ones that have been scanlated by Attractive Fascinante.