TOTTO(guitarist) & Yuuga(vocalist)
Like many of DK's contemporary bands, the band went through a lot of line-up changes for one reason or another. The most famous member change, or drop, is guitarist TOTTO. Although it is hard to 100% confirm, or find legitamate information on the matter, it has been said that TOTTO sexually assaulted a fan (alledgedly). Aside from him being removed from the band, DEViL KiTTY also almost disbanded because of the incident. Since there is not a wealth of information on the subject, it can only be speculated that this happened early on in the band's career since TOTTO is only on one picture and also appears in the promotional poster for their first release. Obviously the band remained together and found several replacements for the role of guitarist. However, the band's image had a permenant scar from his actions.
In addition to the sexual assault incident, Yuuga himself also developed a reputation of not being the nicest person to many of his fans. Most of the accounts of mistreating of fans usually end up being from his reaction to fans touching him while performing (which is not strictly limited to this band or even to just Yuuga himself since there are cases of this happening to other musicians as well). This reputations is also intensified from the lyrical content of DEViL KiTTY's songs, such as "バンザイお洒落系," which sarcastically mocks proto-oshare-kei bands (since that movement began around the same time of DK's first album) as well as mocks the movement's fans and their apparently shallow mindset. Another song that was more than likely written out of spite was "奇形の2ちゃんネラー," based on the title having "2chan" in it. For those of you who aren't aware of what 2chan is, it is pretty much the Japanese version of 4chan. This image board apparently had a lot to say about Yuuga, presumably commentary about his stage personality, since he wrote a song dedicated to them. In addition to this song, DEViL KiTTY's Japanese wikipedia page makes note of problems between Yuuga and 2chan, so some sort of conflict definitely occurred.