The funny thing is that, from what I've learnt from comments here as well as what little of the manga I've seen personally, if one just read the WWB, he would get the impression that "Hey, these chaps are Big Bad material!"
But the impression that the novel reader, one who has no exposure to any of the manga, has of Hameln is that this is a bunch of petty scum that, yes, are pretty awful, but has yet cross the line into more serious criminal acts. It's like a pack of opportunistic backyard bullies who are fairly harmless on their own and is terrible only as the lackeys of greater powers.
Such is very different, imho, from the Hameln we are shown in WWB, brigands no better if not worse than their counterparts in Susukino, people who actually do pose a real threat to their fellow residents. It's easier in any case for the reader to imagine what horrible things these thugs have done to their newbies, in particular to older girls like Isuzu, what with that claim of "success testing" with rape or similar
