I have to be upfront: I NEVER review shows. But I need to tell you how bad this show is. I was a big fan of the original Inuyasha - it was one of the first manga I ever read, and inspired me to read not only more Rumiko Takahashi works (Ranma and Kyokai no Rinne) but more manga in general. When I tell you that Yashahime is nothing more than a blatant disservice to the original manga, understand it is coming from a place of deep care.
Yashahime reminds me of shows like Boruto and Dragon Ball GT, and that's not a compliment. The only thing this show has succeeded in is being a grab for cash that older fans in love with Sesshomaru fell for.
Moroha is the only interesting character, and even then, she's reduced to nothing more than a joke, undervalued by everyone around her including her only family. No one else is even slightly interesting. The twins, Towa and Setsuna, are so one-dimensional it hurts to watch them. Towa is bland, boring, unnecessarily overpowered, and a weak attempt at being "not your average girl". Setsuna has cool attacks, but like her sister, no personality or care for anyone but herself. All three of the girls lack proper motivation to do anything worthwhile in the story - Towa's only care is her sister, Setsuna genuinely doesn't care, and Moroha cares about a debt, which has so far proven to be unrelated to any of the "mysteries" the show attempts to present. When the main characters don't care about the mysteries, though, it makes them impossible to set up, and instead every single plot related mystery has quite literally just been hand-fed to the audience. If the characters don't care, why should I?
The only thing worse than the writing is the pacing. It spends weeks on monster of the week while adding nothing to the show, and then dumps several plot-related things all at once. Say what you will about the original Inuyasha, but at the very least, it did a good job of balancing plot and monster of the week stuff. And speaking of the original, the writers have been holding the original cast over everyone's heads - where oh where can they be? - while not making any of the central characters in the sequel even slightly interested. When the original cast did inevitably show, it was not as the developed characters they became at the end of the original, but as cheap charicatures of their most cartoonish traits. Hell, Shippo hasn't even shown up yet! The question of the twins' mother was also posed, and held as a question, despite it never quite being a mystery. Unfortunately, that lead to Sesshomaru having kids with the small child (aprox 7 or 8) that he took care of in the original. I don't think I have to explain why that's unnerving.
All in all, Yashahime has failed on every front - failed to write engaging characters, failed to write an engaging plot, failed to write compelling mysteries, and failed to make me care. If you're considering watching Yashahime, please take this as a sign NOT TO.