|Hobby||Chatting with Tiara|
|Japanese voice||Arisa Noto|
Cui is Tiara's fairy partner. It doesn't speak human language, but Tiara and it understand each other. Its bark is "Kyui Kyui" or in English version "Cui".
Cui is a white Fairy resembling a puppy with long bushy ears matching its tail. On each ear is a big circle with a line, along with a few parts of hair at the top of the head. Its eyes are dark red, and at it's neck they wears a dark colored bow with thin white lines on each part, and a bright pink gem in the middle.
Cui is very much like a puppy. He/she loves Tiara.
- Eryn referred Cui as a female when she questioned Tiara about her translation from Cui's language, saying "Are you her translator now!?"
- However, in one of the sub-events of the Vile God Route, Tiara referred Cui as a male while she was thanking Ryushin for taking care of Cui under her absence, stating: "Cui tells me you've done quite a lot to him. Thank you very much."
- In Advent Dark Force during a sub-event, it is revealed that Cui's official name is Cuberial.