The meat is a Merman's meat.
The flesh of a Merman, or for that matter, also the flesh of a Siren. It is said that these two siblings species have flesh that is efficacious for immortality. That's the truth.
The state of Roxus's body was forcing her to take such flesh into her mouth, into her body. Roxus wanted to cry. This is the flesh of her earthlings. This is the flesh of the creature she was supposed to protect.
But Kwon Jiyong had decided as the Emperor of the Black Ocean to offer the flesh of the criminal to the Madam to apologize for their sins. Kwon Jiyong raised his pale face, looked straight at Rong and Haoling, who didn't change their cold expressions.
