In 2026, the "Abyss Overflow Phenomenon" occurs frequently in many places around the world. Weird energy penetrates the urban fabric, spawning a large number of Cthulhu-style aberrations (collectively known as "Abyssal Species"). At the same time, it awakens the "sequence genes" in some humans. Awakened people can obtain "Sequence Fragments" to strengthen themselves by hunting Abyssal Species. The official "Anomaly Phenomenon Control Bureau (APB)" was established to suppress the abyss crisis, while private forces such as "Fragment Hunters" and "Sequence Sect" were spawned. The sequence is divided into 9 levels, each level has 100 basic numbers. The higher the number, the weirder the ability. However, "Sequence No. 0" Has never appeared in official records.
