- A-ya and C-ta are childhood friends and neighbors. He meets with C-ta, D-ne, and B-ko almost every day after school in an abandoned classroom to discuss rumors and occult legends. C-ta often speaks for A-ya, and constantly looks for his approval by asking "Right, A-ya?" afterwards. They walk to and from school together.
- C-ta tends to "observe" A-ya. It has also been hinted that C-ta has walked around A-ya's house at night and watch him when he is asleep, to "check for suspicious behavior". A-ya acts indifferent towards C-ta, perhaps even cold, though they usually spend most of their free time together. A-ya seems to be oblivious when it comes to C-ta's feelings.
- When they were kids, C-ta gave A-ya a bunny plushie, which the latter used to play hide and seek alone. In the song "Lonely Hide and Seek" A-ya uses the bunny C-ta had given him as a child to follow Kokkuri-san's demands of playing hide and seek alone. He named the rabbit after C-ta, and stabs the rabbit with a cutter/scissors to continue the game. At the end of the song, it is hinted that A-ya is killed using the same weapon he had given to the rabbit. It is revealed in "Perfect Crime Love Letter" and in the novel that C-ta had been A-ya's killer.
- In the song "Re: Missed Call", A-ya and C-ta reflect on their actions and the Demise Game. The song tells how the two of them had reflected on the previous incidents and wished to change the past. The last few verses of the song reveal that A-ya did care for C-ta, and regret having wished away their boring life. It is not revealed whether these feelings are romantic or not.