Sayaka Koyanagi

Sayaka Koyanagi (小柳紗耶香, Koyanagi Sayaka) is a young girl who formed a group of Collectors to gather a hundred coins.

Appearance
Sayaka is a young girl with long dark hair. She wears a swimsuit top, short pants, long gloves with sleeves, and a collar with a plus symbol. In order to hide her identity, she would wear a hockey mask.

Personality
Sayaka was in love with a female teacher, who had moral doubts about their relationship and Sayaka ended up sharing with a friend, which led to the friend revealing it publicly and the teacher killing herself. After being betrayed, Sayaka started to have trust issues. Because of that, she had a very clear image of what she wanted and received her ability.

Plot
Ikeuchi had brought Claire Aoki and Shuichi Kagaya to join their group. After speaking with Sayaka, Claire agreed to join the group which had a condition she first needs to meet. Sayaka then brought her to a different room and explained her ability. Tying a string of hair around Claire's neck would mean that if she reveals any of their secrets, the string will tighten and kill Claire. The hair soon will turn invisible and part of her body and no one, including Sayaka, can remove it. Sayaka then explained her past with a female teacher and how she spoke with a friend and because of that, the teacher killed herself. Claire showed a picture of her sister and Sayaka told her she knew her, as they used to be in the same school. Claire was speculating she may have learned about them from Ikeuchi, but since Ikeuchi is still alive, it means he hasn't revealed any of their secrets. In the end, Claire decided to join the group.

Power & Abilities
As she has a very clear idea of what she wants, she received an ability that would force the people that made contracts with her to keep her or her friends secrets. She ties a string of her hair around the person's neck, which soon becomes invisible and part of the body. And if the person reveals any secret about them, the string will tighten and kill the person.