Since the early 20th century, monsters with unique personalities have suddenly appeared all over the world. At first, humans tried to resist, but it was impossible to completely drive them away in the face of their immense power. People decided to focus their wisdom on monitoring and analyzing the monsters, leading to the establishment of the "United Nations Monster Surveillance Agency." Led by the indomitable leader, Director Kaido Yuichiro, the agency includes authorities in various fields: monster ecology expert Kobayashi Maru Choji, genius in monster functional analysis Claire Coleman, maverick in monster disaster prevention Kenny Mikoshiba, noble strategist in monster tactics Nikita Tarkovsky, new-generation pioneer in monster linguistics Lulu Du Picard, and the leading authority in monster life sciences Guillermo Marquez. These monster science experts have monitored and analyzed hundreds of monsters, continuing to explore a world where monsters and humans coexist.