Marriagetoxin is a romantic comedy manga about Gero, a young man from a family of assassins who is expected to continue the family business. To avoid this fate, he proposes a contract marriage to a cheerful and mysterious girl named Mei, who is actually a professional poisoner. They agree to fake a relationship to help each other escape their dangerous jobs, but their partnership leads to chaotic adventures and genuine romantic tension. Readers enjoy it for its unique blend of action, humor, and sweet romance, as well as the quirky chemistry between the deadly yet endearing main couple.