All four of these terms are part of the otaku “moe” phenomenon that has been growing in popularity these past few years, and in particular are called “gap-more” traits. Moe is a sort of hard word to define, but it embodies the feeling of attraction or cuteness in a character or even a person. Gap-moe is a particular type of moe which derives its value from a “gap” in the character’s personality. For example, all of the 4 examples I listed above would be considered a type of gap-moe because of the stark contrast between the dere side and their other half. That’s it for the short history lesson!
What I want to do is spread the knowledge and acceptance of not only dere, but Otaku/Akiba culture in general. So my job now is to figure out ways in which to do that!