In the Japanese language, honorifics are those sounds that are added onto people’s first or last names like -chan, -kun, -sama, etc. The honorifics used by characters in Twst have been catalogued here ->
And they are more than sounds: they are also used as a signal of your relationship to the person you’re speaking to and their relationship to you. When we don’t use any honorifics at all, this is called 呼び捨て (yobi-sute). It is used with the kanji for “to call” and “to throw away”, and it is a verb that means “to refer to someone without honorifics”.
Twisted Wonderland uses honorifics to track the evolving relationships of the characters with one another.
In the novels, for example, prefect character Kuroki Yuuya refers to Ace as “Ace-kun” from pages 97 to 179, at which point Ace himself finally says “Just call me Ace”, as Yuuya refuses to make the jump for himself. Yuuya does so for the first time on page 181, while in narration it is explained, “Yobi-sute was a little awkward, but Ace didn’t seem to mind at all. In fact, he looked refreshed.”
Yuuya says Deuce’s name for the first time on page 121, referring to him as “Deuce-kun” until page 197 when Deuce, too, gives Yuuya that push he needs.
It is a literal way to track the progression of the main three as their relationship evolves. Deuce and Ace, for their part, never refer to Yuuya as anything but ‘Yuu’, as insisted upon by Grim.
As Riddle’s abuse of his dorm-mates increases, Cater―who has referred to absolutely everyone, including himself, with some form of honorific up until this point, says “Trey”, as yobisute. This moment is so significant that it is emphasized in the narration.
When Chenya appears before Ace, Deuce, Yuuya and Grim, he refers to Riddle as “Riddle”, and Yuuya reflects, “Chenya speaks of Riddle with a lot of familiarity―he is the only person Yuuya has met who refers to Riddle with yobi-sute…except for Trey.”
This reveals to the main four that Chenya has a history with Riddle, without him ever needing to say so in as many words.
The next time it is referenced is shortly after, when Ace has decided to challenge Riddle for the position of Housewarden. Grim complains about the collar that Riddle is forcing him to wear, and Ace announces, “Don’t worry. When I become house warden, I’ll order Riddle to to remove it.” And Deuce responds, “Oof, already with the yobi-sute…”
And this is not limited to the novels: the use of honorifics is an integral part of every character in the game, with Riddle dropping the “senpai” from Leona’s name in a dramatic moment, Azul dropping “san” from Riddle’s name in a moment of danger and more.
For reference, here is a graph of every character’s use of yobisute as of the second novel:
Twisted Wonderland Reference Note 