WARNING: The following contains spoilers for Episode 12 of Yashahime: Princess Half-Demon, "Night of the New Moon and the Black-Haired Towa" now streaming on Crunchyroll, Funimation, Animelab and Hulu.
Yashahime: Princess Half-Demon has made it very clear that Towa is its central protagonist. Not only does the story revolve around her concerns and motivations, but she is almost always the one to vanquish whatever demons the heroines are fighting. There's a formula to it -- the half-demon princesses fight, gradually become overpowered by the enemy and then Towa unleashes a powerful Hail Mary move that defeats the foe in a single blow. "Night of the New Moon and the Black-Haired Towa" subverts this with a callback to the original Inuyasha -- at least initially.
After several episodes, Konton makes his triumphant return here, still grumbling about aesthetics. While he finds the fact that the princesses are half-demons "distasteful", he doesn't turn his nose up at employing another half-demon of his own: Nikosen. Nikosen was a human sage who became corrupted and has turned into a demonic entity himself, and Konton figures that as a half-demon he should be able to take care of Towa, Setsuna and Moroha. Fight fire with fire.
Normally, the princesses would take care of a villain like this no problem-- but it seems that Towa takes after her Uncle Inuyasha in that she's weakened by the new moon. According to Myoga, this is common for half-demons, if not fully understood. While symptoms vary from individual to individual, Towa and Inuyasha have the same reaction: they revert to human form. Towa is left depowered and helpless in the face of Nikosen.
At first, this seems like a rather welcome chance for Setsuna and Moroha to shine. Moroha in particular finally gets a little more to do in this episode. When Setsuna and Towa set off to find Nikosen, she is already on the trail. When Towa collapses as she reverts to a human state, it's Moroha who initially fends off Nikosen and then ushers Towa to safety. Still, her Kurikaramaru isn't sharp enough to penetrate his hide, and she isn't smart enough to figure out that shooting arrows at his head won't do her any good. Moroha is a strong fighter and skillful in many ways, but she isn't always great at putting two and two together.
In the end, despite Towa being out of commission for the duration of the adventure, she still manages to do what she does best: finish off an enemy with a single powerful move. It's become exceptionally clear that Towa is the strongest of the three by far, and Setsuna and Moroha are coming to rely on her more and more.
Even if Towa ultimately saves the day, as usual, this was a good episode for Moroha and Setsuna. Moroha got to have some agency and protect Towa for a while, and Setsuna showed real genuine concern for her sister-- definitely character growth for someone who's usually so closed off. It's fun when Moroha and Setsuna get something to do, and this episode was no exception -- hopefully, they'll continue to get more action in the weeks to come.