I've just checked some Chinese scans, and I think the manga is not bad. The art is no matched for the game's, but it doesn't look bad either. I'll try to hunt the raw to scanlate it soon.
There were also some interesting things I found while reading the visual novel. Chihaya turned out to be the younger brother of Mariya in Otoboku 1, and he had a twin sister, named Chitose (deceased when they were children).
The secret of Chihaya's boobs has been revealed. The fake boobs are breast pads with the color exactly as human's skin. I assume this is also what Mariya did with Mizuho.