Motto, Ikitai... (YOSHI)

The world is a cruel and confusing place for Mayumi. At the age of thirteen she lost her parents in a car accident. Unable to deal with the overwhelming sadness, hatred, and anger, she only wished she could stop feeling altogether.
Then, five years later, her sister becomes the first target of an incredibly bizarre incident. The victims in this incident lose a body part, without blood loss, after receiving a text message simply indicating the specific body part. The texts appear to come from Mayumi's sister's ex-boyfriend Kanno, but he claims to not be the culprit.
Mayumi works with him to solve the case, but is he truly innocent? Or is the crime related in some convoluted way to the suicide of Kanno's fiance years ago? Or is it related to an unfinished AI program he was writing which may have broken free? And even if this incident is resolved, will Mayumi ever be able to truly heal emotionally amidst the pointless cruelty of the world?