An ex-thief who used her skills from the age of 6 to survive. She is aged around 15 to 16 and is very agile and strong. Kotobuki does not like to act spoiled. She is a war orphan, a 'nameless one', and as such has compassion for other orphans like her. She was raised in an orphanage by a gentle woman named Ann, who she viewed as her 'mother'. The orphanage was burnt down while Kotobuki was out getting Ann medicine, leaving her the sole survivor. She then takes up thievery in order to survive, and is very talented at it though she dislikes it. She meets Raimon during her time as a thief, and though he initially annoys her she ends up falling in love with him. During the story Kotobuki's goal is to find Tsubasa so she can wish the bomb out of his head. She temporarily leaves Raimon while visiting ancient Japan to find Tsubasa, while he must stay due to his bomb. Hil ends up falling in love with Kotobuki as he sees her as a replacement for Ann. At the end, Hil tells her that if she becomes his he would deactivate Raimon's bomb. Hil tries to seduce her several times throughout the story. Kotobuki goes to rescue Raimon after he is kidnapped by the military, and succeeds with the help of Shouka's gang, Yan, and Phere.

At the end, Raimon and Kotobuki are engaged to be married.