Koyori Akutagawa

A white-haired girl who is Tazuna's partner. Before meeting him, she had been put to sleep to conserve her life force, but after having her hand held by Tazuna she woke up and they became Hand Shaker partners. She reminds Tazuna of his younger sister and even though is expressionless and does not speak, she is extremely compassionate and cares very deeply about Tazuna.

(Source: Wikipedia)