When did the event related to Rurichiyo Kasumioji really happen? In Bleach, while Ichigo and the gang invading Hueco Mundo, they keep cutting away to Rurichiyo Kasumioji and her story:


   they save her, kill the guys with the Hollow Swords, and save the head captain.


When did that really happen? Did they help her before or after going there?
It's a filler arc, that does not contain canon material. The anime creators were forced to insert this new arc randomly in the middle of the Hueco Mundo arc as the anime was catching up too fast with the manga.

However, I think it's safe to say that it occurs in the tiny window between Ichigo's training and Orihime's kidnapping, as Ichigo uses his hollow abilites, and Orihime hasn't been kidnapped yet.