>>36984166>tsunderefrom ツンツン (tsun-tsun, “to turn away in disgust”) + デレデレ (dere-dere, “to become lovey-dovey”).
Basically, aggressive/insulting/etc at first/while in the presence of others/etc, but lovely when alone with their loved one/after "character development".
>yanderea portmanteau of 病んでる (yanderu), contraction of 病んでいる (yandeiru), progressive tense of 病む (yamu, “to be sick”), and デレデレ (dere-dere, “to become lovey-dovey, infatuated, lovestruck”).
I can't really explain this one very well, I'm not well versed in the root of the characters but, now-days, they are presented as that love interest that's fucked up in the head and (may) be willing to kill people for their loved one/because they think it's what's better for the one they love, among other stuff.
>>36984211 explains it much better, however. Blue isn't really a Yandere character, just very weird/autistic. 
