Shinichirou decides to look for a job in order to pay his rent, and his teacher suggests that he work for someone at their house, doing housekeeping. However, the person who hired him was Sakuya, a girl who is...

The manga centers on Shin Kiba, a middle school student who accepts his destiny as a human weapon in order to fight evil and protect Japan.

Weak, bullied, and pessimistic about life, that's Setsuna Kashiwagi. On the verge of jumping off a bridge, a mysterious man appears behind him and offers the contract "10 million yen in exchange for your life...