Turn Back The Pendulum 5

A hundred and one years before the Fake Karakura battle, nine years after Urahara took the Twelfth, three souls choke to death on a substance pouring from their mouths. Three shadowed figures observe the deaths, remarking that ordinary souls cannot hold the prototype, and resolve to continue the experiments despite the toll. In the Seireitei, Shinji greets Urahara as he passes with Hiyori and Mayuri, gently reminding him to drop the honorific. Aizen raises the month-long string of disappearances in the Rukongai, where the missing leave their clothes behind. Since a true death would reduce both body and garments to Reishi, the only explanation is that the souls are destabilizing, unable to hold human form, and fading away. The Ninth Division has been assigned to investigate.

Marching through the Rukongai, Kensei Muguruma bristles as his lieutenant Mashiro Kuna questions why a captain should chase an unknown cause and demands they wait for the ten advance guards to report. The bickering breaks when a Hollow attacks a small boy, and Kensei destroys it with his Shikai. Finding the child in tears, he hauls him up, tells him to be glad he is alive, and asks his name. The boy answers Shūhei Hisagi, and Kensei tells him it is a strong name and to stop crying. Mashiro then reappears with unsettling news: she has found ten shihakushō abandoned in the nearby bushes.

The chapter opens the arc's central mystery, revealing hidden experimenters killing souls with a prototype that ordinary spirits cannot contain. It confirms the Rukongai disappearances as souls destabilizing into nothing and puts the Ninth Division on the case. It introduces a young Shūhei Hisagi, saved and named by Kensei, seeding their bond. The discovery of ten empty uniforms belonging to the advance guards signals that the phenomenon has now claimed Shinigami as well.

The fifth Turn Back The Pendulum chapter was adapted across Episode 208, Aizen and the Genius Boy, and Episode 209, Muguruma's 9th Division, Moves Out. It shifts the flashback forward roughly a decade and pivots the story from Urahara's institute to the crisis that produces the Visored.