Kūkū Ketsugō

 (結合 空空, Ketsugō Kūkū) is a that roams the. She is neither a nor a, and can be considered a unique existence due to this. Kūkū is the result of multiple souls converging into a single entity — to be exact, she is the end result of the entire population of Kūzen City, along with the who guarded the city, being combined into a single entity. 200,000 Human and Plus souls, combined using the Shinigami soul as a base template, resulted in Kūkū Ketsugō.