Funny thing actually. Oku Hiroya wrote both of these versions of Hen. Just that he changed the stories abit. This Hen that is beng hosted here is a rather new version. I own the "Akai" volume of Oku Hiroya's Collection work and it has a collection of his earlyish work "Suki" which has almost exactly the same story as the Hen that is currently being hosted. I have also seen the original HEN manga by Oku HIroya which chronicles both the original HEN stories.
Shin0 is both right and wrong, because in the latter half of oku hiroya's HEN series,a similar story of Chizuru and Azumi appears (i think, i'll follow up on this post at a later date). So yea, from my understanding of it i think Oku Hiroya just redrew and rewrote his original Suki story and re-released it as the current Hen that is being hosted.
P.S. Admin if you're wondering why i havent posted till now, its coz i'm actually pretty bogged with work most days :P only have time to click on downloads and read them after hours later. >< so yea. First Post! :P
Laughter is just a fake response when you actually feel pain.