Saikano, volume 3

Shuji and Chise, a teenage couple in a small town, struggle to nurture their relationship while keeping Chise's identity a secret--she's been engineered to be the ultimate fighting weapon for Japans's military force. When Chise chooses to meet Shuji for a date instead of going on a combat mission, her decision has calamitous consequences. While waiting at their rendezvous spot, Chise is shocked to find out Shuji's been with his former girlfriend.