The Last Love Song on This Little Planet (2005)

Quiet, introverted high school girl Chise, who is madly in love with Shuji, a confident, arrogant athlete. They both go to the same high school in Hokkaido, but it takes Chise all of her courage to tell Shuji about her feelings for him. The two hit it off and form a strong, loving bond, which only intensifies when war breaks out in Japan. But Chise has a secret, one so dark, so terrible that it may threaten not only her relationship with Shuji, but also her life, his life and the future of the entire country. For Chise is no ordinary girl, she is the ultimate weapon of mass destruction, a genetically engineered cyborg built specifically for military use - and when she goes into battle she strikes fear in everyone around her, including her own troops.