The mantis by Kotaro Isaka

Picture a mantis raising up its blades. It looks fearsome, but it’s still just a tiny insect. The mantis actually thinks it can win. Even though it’s tiny, it’s still ready to fight to the death. Kabuto is an ordinary guy; stressed with work, hassled by his wife and disrespected by his son. No wonder he visits his doctor so often. Except ‘the Doctor’ is actually his handler, and Kabuto is a hired assassin. The ‘prescriptions’ the Doctor hands over are his unlucky targets. Because although Kabuto may seem like a small man at home, he’s really good at killing people. Kabuto is worn out with the business of murder. He’s trying to pay his way out of the Doctor’s employment with a few last jobs. But the most lucrative contracts involve taking out other professional assassins and his final assignment puts both him and his family in danger.