The title for this chapter (証果, "shouka") is a very specific, very obscure Buddhist term that means "to attain a state of enlightenment as a result of your training". It's a clear reference to Shizuno. I decided it was better to just leave it untranslated and put an explanatory note. This is a different term than the common way to say "enlightenment" in Buddhism, which is 菩提 "bodhi".
The flashback scene in this chapter was already shown (for the most part) in chapters 19 and 20 of Achiga-hen.