Although bright and cheerful, Karin has a tragic past, besides suffering from her father's disappearance, she has lost her mother at an early age. With the help from friends, she has recovered, but the past tragedies are coming back to haunt her. A mysterious organization is aiming to take her life, and to survive, she entered the fray as a sniper.

Following hints and leads given to her by Tsukasa, a man who seems to know more than he is willing to divulge, Karin is forced to take the path to confront the truth behind her father's disappearance and the threats of the mysterious organization.

[from Wikipedia]