this is an embarassment to the real characters in this fine story. As anyone knows Haramura has a large bust a very large one and this author appears to be afraid of oppai. A sad example of poor work.
In response to what BlueMoonCircle says, while Haramura and many other girls have very large breasts at the current point of the manga, this was not always the case. Her breasts were somewhat large at the beginning of story and grew to be huge as the artist decided to emphasize them more as time went on. This doujin was written back in 2013, when she would've been much smaller than she is now. I know the comment is likely in jest, but I think it's still worth pointing out.