Poison Master Hikaru Gero is about to take on his most challenging assignment yet--getting married! But after training his entire life to become one of the world's deadliest assassins, Gero couldn't be more clueless when it comes to the art of dating. Thankfully, marriage swindler Mei Kinosaki knows everything there is to know about love, and together, this unlikely pair is going to do whatever it takes to get Gero hitched--even if they have to take on the entire criminal underworld in the process!

Not long after accepting his latest assignment to protect Hamster Master Arashiyama, Gero is struck by a surprise attack from the deadly Hit Man Hunter! To make matters worse, Arashiyama's life becomes threatened by the head of the Beast Clan, which means Gero will have to risk walking into the heart of this rival clan's territory if he wants to have any hope of keeping her safe...