Marriage Toxin is a Japanese manga series written by Joumyaku and illustrated by Mizuki Yoda. It follows Gero, a young assassin from a long line of poison experts, who is pressured to continue the family line. To preserve his sister's happiness, he teams up with a skilled marriage swindler to help him find a suitable bride while dealing with dangerous enemies and chaotic romantic situations. The series blends action, comedy, and romance.