The "little text" is ruby, normally it's used to explain the correct reading of kanji, but here the author is probably using it to make up their own term (A practice which is infamous for being abused by LN writers). So literal meaning is that "strange creatures" and "creepy friends" are interchangeable terms.
The little text is Furigana or in wider term, like StrangeStripes said, a Ruby.
If you see most of chuuniby-- *cough* fantasy japanese story, either manga, novel or light novel, this will be used to put a "cool" term, that the author wants to use, and the (kinda) simple description on it. Here's one general example from Fate series :
The kanji read as : yakusokusareta shouri no ken, but the term that will be use by the author/mangaka is the small text : excalibur
Weird? Like certain anime priest once said : "you get used to it".