Please don't associate the manga with the real novel or anime adaption. This manga is 100% fanservice.

The manga is basically just ecchi. There was no need for a manga version to start with since the series is derived from a novel. Would definitely not advise anyone to read unless they wanted to read hentai.

The manga does indeed include a portion of the original plot, however the intensity of the plot is weakened by the constant fan-service. The male characters such as Satoru, Shun, and Mamoru are left in the dust.