is demon slayer: kimetsu no yaiba episode 17 filler?

The Twelve Kizuki, directly subordinate to Muzan Kibutsuji, are here…When Tanjiro slays the mother of the Spider Demons of Mount Natagumo, he learns that a demon who might become the key to turning Nezuko back into a human could be in this very forest. Despite how battered Inosuke is, he heads deeper into the forest with Tanjiro.

Meanwhile, Zenitsu trudges forlornly through the woods, only to encounter a human-headed spider.