Marriage Toxin, Vol. 3 by Joumyaku

Gero may be a master assassin, but he’s not exactly killing it in the romance department! Can marriage swindler Kinosaki help him find true love?

Poison Master Hikaru Gero is taking on his toughest assignment yet—getting married! Gero couldn’t be more clueless when it comes to dating, but thankfully, marriage swindler Mei Kinosaki knows everything there is to know about love. Together, this unlikely pair will do whatever it takes to get Gero hitched—even if they have to take on the entire criminal underworld in the process!

After Kinosaki sets Gero up as bodyguard for Shiori Ureshino—the daughter of a high-profile CEO—Gero’s assassin skills are pushed to the limit as he tries to prevent Sound Master Naruko from turning Ureshino’s university camping trip into an all-out horror show!