is demon slayer: kimetsu no yaiba episode 25 filler?

Tanjiro, who has been going through rehabilitation training at the Butterfly Mansion, works hard to keep up his Total Concentration Breathing all day long. Though at first, he's helpless against Kanao, a swordswoman in his class who’s training him, he slowly but surely begins to make some headway.

Seeing Tanjiro devote himself to training every single day, Zenitsu and Inosuke finally resume training as well, but…