Given the circumstances, writing an extremely good cliffhanger is probably the best bet (my terrible attempt):
Chapter 685: Return to nothing, bleach.
Yhwach though defeated, is still alive. Aizen is no where to be found. Ichigo, finally feeling the damage Yhwach has given to him collapses. Suddenly a huge explosion appears, Yhwach's corpse begins to transform and Ichigo stands yet again preparing for battle.
The corpse implodes, revealing Aizen's silhouette. Ichigo asks if it is him, and he says that he has again transformed, thanks to Yhwach. Ichigo begins to leave when Aizen grabs him from the behind on the shoulder.
Ichigo, looking dazzled, asking him why he's doing this. Aizen says that he's confused, and Ichigo doesn't understand. Finally, Aizen says, "... since when where you under the impression, that we were ever finished?"
[ Panels of every encounter between Ichigo and Aizen are shown, revealing that all of Ichigo's fights with every non-hollow character in the Manga has actually been with Aizen. ]
Aizen then says
"Bankai."
[end]