The Hollowfication Incident is a major incident detailing the history of the Visored's creation and the ascendancy and fall of Kisuke Urahara within the 13 Division Imperial Guards (Gotei 13). It further goes into the onset of the first attempts of Hollowfication by Sōsuke Aizen over one hundred years ago.
The incident started with the appointment of Kisuke Urahara as captain of the 12th Division after the promotion of Kirio Hikifune to the Royal Guard. Using his new status, he creates the Shinigami Research and Development Institute in order to put his inventions to good use.
Nine years later, Aizen conducts Hollowfication experiments on residents within the Wandering Soul City (Rukongai) prompting an investigation from the 13 DIG. The 9th Division are tasked with the mission, but most of its highly ranked officers are cut down and the captain and lieutenant are Hollowfied. This prompts further investigation and the team that are sent out are also subjected to the experiments. The arrival of Urahara saves them from slaughter, but Aizen escapes. When he fails to save them, Urahara is arrested and charged with the crimes. With the help of Yoruichi Shihōin he and the Visored escape to the Human World.