Gemini

Gemini are tools provided to the original five contestants, Ink, Aether, Rae, Beth and Liza and their respective Contacts.

Each Gemini is a simple PDA, showing the date (March 19) and is able to comminucate with one Contact on the other end.

As of chapter 25, only two Gemini remains, with one being destroyed by its owner, one being destroyed when a bomb went off and the third one was disposed off by the owner.

Of the remaining two Gemini, one has been hijacked by Sent in order to comminucate with the owner of the Gemini in private while it's unknown how much use Aether's has, as her father seems to care little for her, according to her.