Yui Kanakura (かなくら ユイ, Kanakura Yui) is a childhood friend of Raku as well as his current homeroom teacher. Yui is also the head of the Chinese mafia group, Char Siu (Chinese: 叉燒, Chāshāo). Yui is also in possession of a fourth key but has confirmed to Raku that she is not the girl he had made a promise with ten years prior.