Marriage Toxin

Those who have honed their family's techniques for hundreds of years are known as "masters."
Among them is Hikaru Gero, a young man who inherits the bloodline of the Gero family, one of the strongest among them.
For someone who had been involved in the underworld, "marriage" was something far removed from his life.
However, in order to prevent the family bloodline from dying out, the head of the Gero family informed his sister that he would be forced to bear an heir.
It was at this time that Gero met Kinosaki Mei, who would become his target for his work.
To protect his sister, Gero decides to get married himself and immediately asks Shirosaki, a marriage expert, to help him with his search for a spouse.
And so, Gero embarks on his first ever extremely difficult mission: "marriage hunting"...!?
My goal is the perfect marriage...
The ultimate buddy duo, Hikaru Gero and Mei Shirosaki, take on the world's toughest matchmaking battle action!!