Evolution?! The Menace of the Final Sword Fiend

As all the Shinigamis' Zanpakuto are struggling fighting a Sword Fiend, a flashback of the day before to the events that lead to this battle is shown. Kazeshini is battling with a Sword Fiend who has been cornered by 9th division, as they get separated Kazeshini is about to give the fatal blow the Sword Fiend turns back to a regular sword. Later on when Kazeshini, Zabimaru, Hozukimaru and Fuji Kujaku (Ruriiro Kujaku) gather together they discuss how they found "that Sword Fiend". They discuss how the Sword Fiend from before turn back because he had lost so much reiatsu. We learn how the Zanpakuto only so much reiatsu that they receive, when the gained their physical forms and once they lose all that reiatsu they turn back to swords. "That Sword Fiend" apparently can steal other Zanpakutos reiatsu and that he has surpassed his masters strength. The Shinigamis' Zanpakuto then decided to take care of "that Sword Fiend" so as not to put their masters at risk. The fight continues, and just as the zanpakuto are about to lose, their masters show up and tell them to not fight alone. The zanpakuto then turn into their swords and then fight with their masters. As the fight continues, the zanpakuto give what little reiatsu they have left to Renji so that he can activate his Bankai, which he then uses to grab the Sword Fiend with its teeth and shoot it with his cannon at point-blank range. The episode ends with the zanpakuto in their original sword forms.