Zenno's City was Holt City, so it was understandable that they had the most progress.
Holt City was one of the strongest and longest-lasting territories in the human territory, after all, and they were also one of the more open-minded ones.
They were the first to create an organized team of healers, plant experts, and alchemists to figure out more about the disease. It would take them years to get any real progress, but they could be said to be the forerunners of this one.
Zenno was not yet a top Alchemist at the time, but he was part of the team. It was just that he was obviously under oath to protect the city's interest. However, his oath was naturally flexible due to his occupation and his level.
After an agreement through posts with the other side, Zenno was allowed to share the things he learned during that time with Alterra.
